Positive resist composition, method of forming resist pattern, and polymeric compound

ABSTRACT

A positive resist composition including a base component (A) which exhibits increased solubility in an alkali developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure, the base component (A) including a polymeric compound (A1′) containing an acid dissociable, dissolution inhibiting group within the structure thereof and including a structural unit (a0) represented by general formula (a0-1) (R 2  represents a divalent linking group, and A″ represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom) and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group; or a polymeric compound (Al) including the structural unit (a0) and a structural unit (al) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group.

TECHNICAL FIELD

The present invention relates to a novel polymeric compound which can beused as a base component for a positive resist composition, a positiveresist composition containing the polymeric compound, and a method offorming a resist pattern using the positive resist composition. Priorityis claimed on Japanese Patent Application Nos. 2008-251597 and2008-251598, filed Sep. 29, 2008, and Japanese Patent Application No.2008-254847, filed Sep. 30, 2008, the contents of which are incorporatedherein by reference.

BACKGROUND ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure of radial rays such as light or electronbeam through a mask having a predetermined pattern, followed bydevelopment, thereby forming a resist pattern having a predeterminedshape on the resist film.

A resist material in which the exposed portions become soluble in adeveloping solution is called a positive-type, and a resist material inwhich the exposed portions become insoluble in a developing solution iscalled a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have leadto rapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength of the exposure light source. Conventionally, ultravioletradiation typified by g-line and i-line radiation has been used, butnowadays KrF excimer lasers and ArF excimer lasers are starting to beintroduced in mass production. Furthermore, research is also beingconducted into lithography techniques that use an exposure light sourcehaving a wavelength shorter than these excimer lasers, such as F₂excimer lasers, electron beam, extreme ultraviolet radiation (EUV), andX-ray.

Resist materials for use with these types of exposure light sourcesrequire lithography properties such as a high resolution capable ofreproducing patterns of minute dimensions, and a high level ofsensitivity to these types of exposure light sources.

As a resist material that satisfies these conditions, a chemicallyamplified composition is used, which includes a base material componentthat exhibits a changed solubility in an alkali developing solutionunder the action of acid and an acid generator that generates acid uponexposure.

For example, a chemically amplified positive resist contains, as a basecomponent (base resin), a resin which exhibits increased solubility inan alkali developing solution under action of acid, and an acidgenerator is typically used. If the resist film formed using the resistcomposition is selectively exposed during formation of a resist pattern,then within the exposed portions, acid is generated from the acidgenerator, and the action of this acid causes an increase in thesolubility of the resin component in an alkali developing solution,making the exposed portions soluble in the alkali developing solution.

Currently, resins that contain structural units derived from(meth)acrylate esters within the main chain (acrylic resins) are nowwidely used as base resins for resists that use ArF excimer laserlithography, as they exhibit excellent transparency in the vicinity of193 nm (for example, see Patent Document 1). Here, the term“(meth)acrylic acid” is a generic term that includes either or both ofacrylic acid having a hydrogen atom bonded to the α-position andmethacrylic acid having a methyl group bonded to the α-position. Theterm “(meth)acrylate ester” is a generic term that includes either orboth of the acrylate ester having a hydrogen atom bonded to theα-position and the methacrylate ester having a methyl group bonded tothe α-position. The term “(meth)acrylate” is a generic term thatincludes either or both of the acrylate having a hydrogen atom bonded tothe α-position and the methacrylate having a methyl group bonded to theα-position.

Further, in order to improve various lithography properties, a baseresin having a plurality of structural units is currently used for achemically amplified resist. For example, in the case of a positiveresist, a base resin containing a structural unit having an aciddissociable, dissolution inhibiting group that is dissociated by theaction of acid generated from the acid generator, a structural unithaving a polar group such as a hydroxyl group, a structural unit havinga lactone structure, and the like is typically used. Among thesestructural units, a structural unit having a lactone structure isgenerally considered as being effective in improving the adhesionbetween the resist film and the substrate, and increasing thecompatibility with an alkali developing solution, thereby contributingto improvement in various lithography properties.

[Documents of Related Art]

[Patent Documents]

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2003-241385

[Patent Document 2] Japanese Unexamined Patent Application, FirstPublication No. 2006-016379

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

As further progress is made in lithography techniques and theapplication field for lithography techniques expands, development of anovel material for use in lithography will be desired. For example, asminiaturization of resist patterns progress, improvement will bedemanded for resist materials with respect to various lithographyproperties such as resolution and the like.

The pattern shape is one of such lithography properties. In theformation of a resist pattern using a conventional resist composition,when the mask size (e.g., the hole diameter of a hole pattern, or theline width of a line and space pattern) is changed, the amount of lightirradiated on exposed portions is changed. As a result, pattern collapseof the formed pattern is likely to occur. Such a problem is likely tooccur in the formation of a fine pattern with a narrow pitch. Forexample, when a hole pattern having a hole diameter of about no morethan 100 nm is formed, the circularity of the holes is likely to bedeteriorated, and improvement thereof has been demanded.

The present invention takes the above circumstances into consideration,with an object of providing a novel polymeric compound which can be usedas a base component for a positive resist composition, a compound usefulas a monomer for the polymeric compound, a positive resist compositioncontaining the polymeric compound, and a method of forming a resistpattern using the positive resist composition.

Means for Solving the Problems

For solving the above-mentioned problems, the present invention employsthe following aspects.

Specifically, a first aspect of the present invention is a positiveresist composition including a base component (A) which exhibitsincreased solubility in an alkali developing solution under action ofacid and an acid-generator component (B) which generates acid uponexposure,

the base component (A) including a polymeric compound (A1′) containingan acid dissociable, dissolution inhibiting group within the structurethereof and including a structural unit (a0) represented by generalformula (a0-1) shown below and a structural unit (a2) derived from anacrylate ester containing a lactone-containing cyclic group exclusive ofthe structural unit (a0); or a polymeric compound (A1) including astructural unit (a0) represented by general formula (a0-1) shown belowand a structural unit (a1) derived from an acrylate ester containing anacid dissociable, dissolution inhibiting group exclusive of thestructural unit (a0) and the structural unit (a2).

In the formula, R¹ represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R² represents a divalent linking group;each R′ independently represents a hydrogen atom, an alkyl group of 1 to6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or —COOR″,wherein R″ represents a hydrogen atom or an alkyl group; and A″represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5carbon atoms which may contain an oxygen atom or a sulfur atom.

A second aspect of the present invention is a method of forming a resistpattern, including applying a positive resist composition according tothe first aspect to a substrate to form a resist film, subjecting theresist film to exposure, and subjecting the resist film to alkalideveloping to form a resist pattern.

A third aspect of the present invention is a polymeric compoundincluding a component (A1′) containing an acid dissociable, dissolutioninhibiting group within the structure thereof and including a structuralunit (a0) represented by general formula (a0-1) shown below and astructural unit (a2) derived from an acrylate ester containing alactone-containing cyclic group exclusive of the structural unit (a0);or a component (A1) including a structural unit (a0) represented bygeneral formula (a0-1) shown below and a structural unit (a1) derivedfrom an acrylate ester containing an acid dissociable, dissolutioninhibiting group exclusive of the structural unit (a0) and thestructural unit (a2).

In the formula, R¹ represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R² represents a divalent linking group;each R′ independently represents a hydrogen atom, an alkyl group of 1 to6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or —COOR″,wherein R″ represents a hydrogen atom or an alkyl group; and A″represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5carbon atoms which may contain an oxygen atom or a sulfur atom.

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified.

The term “alkylene group” includes linear, branched or cyclic divalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with halogen atoms.Examples of halogen atoms include fluorine atoms, chlorine atoms,bromine atoms and iodine atoms.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a groupin which part or all of the hydrogen atoms of an alkyl group or analkylene group have been substituted with a fluorine atom.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (resin, polymer, copolymer).

A “structural unit derived from an acrylate ester” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of an acrylate ester.

The term “acrylate ester” is a generic term that includes acrylateesters having a hydrogen atom bonded to the carbon atom on theα-position, and acrylate esters having a substituent (an atom other thana hydrogen atom or a group) bonded to the carbon atom on the α-position.Examples of the substituent bonded to the carbon atom on the α-positioninclude an alkyl group of 1 to 5 carbon atoms, a halogenated alkyl groupof 1 to 5 carbon atoms and a hydroxyalkyl group.

Hereafter, an alkyl group of 1 to 5 carbon atoms and a halogenated alkylgroup of 1 to 5 carbon atoms are frequently referred to as a lower alkylgroup and a halogenated lower alkyl group, respectively. A carbon atomon the α-position of an acrylate ester refers to the carbon atom bondedto the carbonyl group, unless specified otherwise.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

Effects of the Invention

According to the present invention, there are provided a novel polymericcompound which can be used as a base component for a positive resistcomposition, a positive resist composition containing the polymericcompound, and a method of forming a resist pattern using the positiveresist composition.

BEST MODE FOR CARRYING OUT THE INVENTION

<<Positive Resist Composition>>

The positive resist composition of the present invention (hereafter,frequently referred to simply as “resist composition”) includes a basecomponent (A) (hereafter, referred to as “component (A)”) which exhibitsincreased solubility in an alkali developing solution under action ofacid and an acid-generator component (B) (hereafter, referred to as“component (B)”) which generates acid upon exposure.

In the positive resist composition, when radial rays are irradiated(when exposure is conducted), acid is generated from the component (B),and the solubility of the component (A) in an alkali developing solutionis increased by the action of the generated acid. Therefore, in theformation of a resist pattern, by conducting selective exposure of aresist film formed by using the positive resist composition of thepresent invention, the solubility of the exposed portions in an alkalideveloping solution is increased, whereas the solubility of theunexposed portions in an alkali developing solution is unchanged, andhence, a resist pattern can be formed by alkali developing.

Here, the term “base component” refers to an organic compound capable offorming a film. As the base component, an organic compound having amolecular weight of 500 or more can be preferably used. When the organiccompound has a molecular weight of 500 or more, the film-forming abilityis improved, and a resist pattern of nano level can be easily formed.

The “organic compound having a molecular weight of 500 or more” whichcan be used as a base component is broadly classified into non-polymersand polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a non-polymerhaving a molecular weight in the range of 500 to less than 4,000 isreferred to as a low molecular weight compound.

As a polymer, any of those which have a molecular weight of 2,000 ormore is used. Hereafter, a polymer having a molecular weight of 2,000 ormore is referred to as a polymeric compound. With respect to a polymericcompound, the “molecular weight” is the weight average molecular weightin terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC). Hereafter, a polymeric compound isfrequently referred to simply as a “resin”.

<Component (A)>

[Polymeric Compound (A1) and Polymeric Compound (A1′)]

In the positive resist composition of the present invention, thecomponent (A) includes the polymeric compound (A1) or the polymericcompound (A1′).

The polymeric compound (A1′) (hereafter, referred to as “component(A1′)”) includes a structural unit (a0) represented by general formula(a0-1) and a structural unit (a2) derived from an acrylate estercontaining a lactone-containing cyclic group exclusive of the structuralunit (a0), and the polymeric compound (A1′) contains an aciddissociable, dissolution inhibiting group within the structure thereof.

The component (A1′) preferably includes a structural unit (a1) derivedfrom an acrylate ester containing an acid dissociable, dissolutioninhibiting group, as well as the structural units (a0) and (a2).

Furthermore, the component (A1′) preferably includes a structural unit(a3) derived from an acrylate ester containing a polar group-containingaliphatic hydrocarbon group, as well as the structural units (a0) and(a2), or the structural units (a0), (a1) and (a2).

The polymeric compound (A1) (hereafter, referred to as “component (A1)”)includes a structural unit (a0) represented by general formula (a0-1)and a structural unit (a1) derived from an acrylate ester containing anacid dissociable, dissolution inhibiting group exclusive of thestructural unit (a0) and the structural unit (a2).

The component (A1) preferably includes the aforementioned structuralunit (a2), as well as the structural units (a0) and (a1).

Furthermore, the component (A1) preferably includes the aforementionedstructural unit (a3), as well as the structural units (a0) and (a1), orthe structural units (a0), (a1) and (a2).

(Structural Unit (a0))

In formula (a0-1), R¹ represents a hydrogen atom, a lower alkyl group ora halogenated lower alkyl group.

The lower alkyl group for R¹ is preferably a linear or branched alkylgroup of 1 to 5 carbon atoms, and specific examples include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, and a neopentyl group.

The halogenated lower alkyl group for R¹ is a group in which part of orall of the hydrogen atoms of the aforementioned alkyl group issubstituted with halogen atoms. Examples of halogen atoms includefluorine atoms, chlorine atoms, bromine atoms and iodine atoms, andfluorine atoms are particularly desirable.

As R¹, a hydrogen atom, a lower alkyl group or a fluorinated alkyl groupis preferable, and a hydrogen atom or a methyl group is particularlydesirable in terms of industrial availability.

In general formula (a0-1), R² a divalent linking group.

Preferable examples of R² include a divalent hydrocarbon group which mayhave a substituent, and a divalent linking group containing a heteroatom.

A hydrocarbon “has a substituent” means that part or all of the hydrogenatoms within the hydrocarbon group is substituted with groups or atomsother than hydrogen atom.

The hydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group. An “aliphatic hydrocarbon group” refers to ahydrocarbon group that has no aromaticity.

The aliphatic hydrocarbon group may be saturated or unsaturated. Ingeneral, the aliphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,and most preferably 1 or 2.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—,an ethylene group [—(CH₂)₂—, a trimethylene group [—(CH₂)₃—, atetramethylene group [—(CH₂)₄— and a pentamethylene group [—(CH₂)₅—.

As a branched aliphatic hydrocarbon group, a branched alkylene group ispreferable, and specific examples include alkylmethylene groups such as—CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—,—C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as—CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and—C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and—CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as—CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. As the alkyl group withinthe alkylalkylene group, a linear alkyl group of 1 to 5 carbon atoms ispreferable.

The linear or branched aliphatic hydrocarbon group (chain-like aliphatichydrocarbon group) may or may not have a substituent. Examples ofsubstituents include a fluorine atom, a fluorinated lower alkyl group of1 to 5 carbon atoms, and an oxygen atom (=O).

As examples of the hydrocarbon group containing a ring in the structurethereof, a cyclic aliphatic hydrocarbon group (a group in which twohydrogen atoms have been removed from an aliphatic hydrocarbon ring),and a group in which the cyclic aliphatic hydrocarbon group is bonded tothe terminal of the aforementioned chain-like aliphatic hydrocarbongroup or interposed within the aforementioned chain-like aliphatichydrocarbon group, can be given.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic group, a group in which twohydrogen atoms have been removed from a monocycloalkane of 3 to 6 carbonatoms is preferable. Examples of the monocycloalkane includecyclopentane and cyclohexane.

As the polycyclic group, a group in which two hydrogen atoms have beenremoved from a polycycloalkane of 7 to 12 carbon atoms is preferable.Examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of substituents include a lower alkyl group of 1to 5 carbon atoms, a fluorine atom, a fluorinated lower alkyl group of 1to 5 carbon atoms, and an oxygen atom (=0).

With respect to a divalent linking group containing a hetero atom, ahetero atom is an atom other than carbon and hydrogen, and examplesthereof include an oxygen atom, a nitrogen atom, a sulfur atom and ahalogen atom.

Specific examples of the divalent linking group containing a hetero atominclude divalent non-hydrocarbon groups containing a hetero atom, suchas —O—, —C(═O)—, —C(═O)—O—, a carbonate bond (—O—C(═O)—O—), —S—,—S(═O)₂—, —S(═O)₂—O—, —NH—, —NR⁰⁴—(R⁰⁴ represents a substituent such asan alkyl group or an acyl group), —NH—C(═O)—, and ═N—. Further, acombination of any one of these “divalent non-hydrocarbon groupscontaining a hetero atom” with a divalent hydrocarbon group can also beused. As examples of the divalent hydrocarbon group, the same groups asthose described above for the hydrocarbon group which may have asubstituent can be given, and a linear or branched aliphatic hydrocarbongroup is preferable.

R² may or may not have an acid dissociable portion in the structurethereof. An “acid dissociable portion” refers to a portion within theorganic group which is dissociated from the organic group by action ofacid generated upon exposure. When R² group has an acid dissociableportion, it preferably has an acid dissociable portion having a tertiarycarbon atom.

In the present invention, as the divalent linking group for R², analkylene group, a divalent aliphatic cyclic group or a divalent linkinggroup containing a hetero atom is preferable. Among these, an alkylenegroup is particularly desirable.

When R² represents an alkylene group, it preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3. Specific examples of alkylene groups include theaforementioned linear alkylene groups and branched alkylene groups.

When R² represents a divalent aliphatic cyclic group, as the aliphaticcyclic group, the same aliphatic cyclic groups as those described abovefor the “aliphatic hydrocarbon group containing a ring in the structurethereof” can be used.

As the aliphatic cyclic group, a group in which two hydrogen atoms havebeen removed from cyclopentane, cyclohexane, norbornane, isobornane,adamantane, tricyclodecane or tetracyclododecane is particularlydesirable.

When R² represents a divalent linking group containing a hetero atom,preferable examples of linking groups include —O—, —C(═O)—O—, —C(═O)—,—O—C(═O)—O—, —C(═O)—NH—, —NH— (H may be replaced with a substituent suchas an alkyl group, an acyl group or the like), —S—, —S(═O)₂—,—S(═O)₂—O—, a group represented by the formula -A-O—B—, and a grouprepresented by the formula -[A-C(═O)—O]_(m)—B—. Herein, each of A and Bindependently represents a divalent hydrocarbon group which may have asubstituent, and m represents an integer of 0 to 3.

When R² represents —NH—, H may be replaced with a substituent such as analkyl group, an acyl group or the like. The substituent (an alkyl group,an acyl group or the like) preferably has 1 to 10 carbon atoms, morepreferably 1 to 8, and most preferably 1 to 5.

In the group represented by the formula -A-O—B— or -[A—C(═O)—O]_(m)—B—,each of A and B independently represents a divalent hydrocarbon groupwhich may have a substituent.

Examples of divalent hydrocarbon groups for A and B which may have asubstituent include the same groups as those described above for the“divalent hydrocarbon group which may have a substituent” usable as R².

As A, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As B, a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula -[A-C(═O)—O]_(m)—B—, mrepresents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

In general formula (a0-1), A″ represents an oxygen atom (—O—), a sulfuratom (—S—), or an alkylene group of 1 to 5 carbon atoms which maycontain an oxygen atom (—O—) or a sulfur atom (—S—).

As the alkylene group of 1 to 5 carbon atoms for A″, a linear orbranched alkylene group is preferable, and examples thereof include amethylene group, an ethylene group, an n-propylene group and anisopropylene group.

Examples of alkylene groups that contain an oxygen atom or a sulfur atominclude the aforementioned alkylene groups in which —O— or —S— is bondedto the terminal of the alkylene group or interposed within the alkylgroup. Specific examples of such alkylene groups include —O—CH₂—,—CH₂—O—CH₂—, —S—CH₂—, and —CH₂—S—CH₂—.

As A″, an alkylene group of 1 to 5 carbon atoms or —O— is preferable,more preferably an alkylene group of 1 to 5 carbon atoms, and mostpreferably a methylene group.

In general formula (a0-1), each R′ independently represents a hydrogenatom, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6carbon atoms or —COOR″.

The alkyl group for R′ is preferably a linear alkyl group or a branchedalkyl group. Specific examples include a methyl group, ethyl group,propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butylgroup, pentyl group, isopentyl group, neopentyl group and hexyl group.Among these, a methyl group or ethyl group is preferable, and a methylgroup is particularly desirable.

The alkoxy group for R′ is preferably a linear alkoxy group or abranched alkoxy group. Specific examples of the alkoxy groups includethe aforementioned alkyl groups for R′ having an oxygen atom (—O—)bonded thereto.

In the formula —COOR″, R″ represents a hydrogen atom or an alkyl group.

The alkyl group for R″ may be linear, branched or cyclic, and preferablyhas 1 to 15 carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used.

Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane andcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

In general formula (a0-1), the two R′ may be the same or different fromeach other

In terms of industrial availability, R′ is preferably a hydrogen atom oran alkoxy group

Specific examples of the structural unit (a0) are shown below.

In the formulas, R¹ and A″ are the same as defined above; and R²′represents a linear or branched alkylene group.

The linear or branched alkylene group for R²′ preferably has 1 to 10carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,still more preferably 1 to 3, and most preferably 1 or 2.

A″ is preferably a methylene group, an oxygen atom (—O—) or a sulfuratom (—S—), and is most preferably a methylene group.

As the structural unit (a0), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In terms of achieving excellent properties with respect to MEF, theshape of a formed resist pattern, in-plane uniformity (CDU), line widthroughness (LWR) and the like in the formation of a resist pattern usinga positive resist composition containing the component (A1) or (A1′),the amount of the structural unit (a0) within the component (A1) or(A1′), based on the combined total of all structural units constitutingthe component (A1) or (A1′) is preferably 1 to 60 mol %, more preferably5 to 50 mol %, still more preferably 10 to 40 mol %, and most preferably15 to 30 mol %.

(Structural Unit (a1))

The structural unit (a1) is a structural unit derived from an acrylateester containing an acid dissociable, dissolution inhibiting group whichdoes not fall under the category of the aforementioned structural unit(a0) and the structural unit (a2) described later.

The structural unit (a1) “does not fall under the category of theaforementioned structural units (a0) and (a2)” means that a structuralunit which falls under the category of the aforementioned structuralunit (a0) or (a2) and contains an acid dissociable, dissolutioninhibiting group is not a structural unit (a1).

As the acid dissociable, dissolution inhibiting group in the structuralunit (a1), any of the groups that have been proposed as aciddissociable, dissolution inhibiting groups for the base resins ofchemically amplified resists can be used, provided the group has analkali dissolution-inhibiting effect that renders the entire component(A1) or (A1′) insoluble in an alkali developing solution prior todissociation, and then following dissociation by action of acid,increases the solubility of the entire component (A1) or (A1′) in thealkali developing solution. Generally, groups that form either a cyclicor chain-like tertiary alkyl ester with the carboxyl group of the(meth)acrylic acid, and acetal-type acid dissociable, dissolutioninhibiting groups such as alkoxyalkyl groups are widely known. Here, theterm “(meth)acrylate ester” is a generic term that includes either orboth of the acrylate ester having a hydrogen atom bonded to theα-position and the methacrylate ester having a methyl group bonded tothe α-position.

Here, a tertiary alkyl ester describes a structure in which an ester isformed by substituting the hydrogen atom of a carboxyl group with achain-like or cyclic tertiary alkyl group, and a tertiary carbon atomwithin the chain-like or cyclic tertiary alkyl group is bonded to theoxygen atom at the terminal of the carbonyloxy group (—C(O)—O—). In thistertiary alkyl ester, the action of acid causes cleavage of the bondbetween the oxygen atom and the tertiary carbon atom.

The chain-like or cyclic alkyl group may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups”.

Examples of tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups include aliphatic branched, acid dissociable,dissolution inhibiting groups and aliphatic cyclic group-containing aciddissociable, dissolution inhibiting groups.

The term “aliphatic branched” refers to a branched structure having noaromaticity. The “aliphatic branched, acid dissociable, dissolutioninhibiting group” is not limited to be constituted of only carbon atomsand hydrogen atoms (not limited to hydrocarbon groups), but ispreferably a hydrocarbon group. Further, the “hydrocarbon group” may beeither saturated or unsaturated, but is preferably saturated.

As an example of the aliphatic branched, acid dissociable, dissolutioninhibiting group, for example, a group represented by the formula—C(R⁷¹)(R⁷²)(R⁷³) can be given (in the formula, each of R⁷¹ to R⁷³independently represents a linear alkyl group of 1 to 5 carbon atoms).The group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³) preferably has 4to 8 carbon atoms, and specific examples include a tert-butyl group, a2-methyl-2-butyl group, a 2-methyl-2-pentyl group and a3-methyl-3-pentyl group. Among these, a tert-butyl group is particularlydesirable.

The term “aliphatic cyclic group” refers to a monocyclic group orpolycyclic group that has no aromaticity.

The “aliphatic cyclic group” within the structural unit (a1) may or maynot have a substituent. Examples of substituents include lower alkylgroups of 1 to 5 carbon atoms, lower alkoxy groups of 1 to 5 carbonatoms, fluorine atom, fluorinated lower alkyl groups of 1 to 5 carbonatoms, and oxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituentsis not limited to be constituted from only carbon and hydrogen (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated. Furthermore, the “aliphatic cyclic group”is preferably a polycyclic group.

As such aliphatic cyclic groups, groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane which may or maynot be substituted with a lower alkyl group, a fluorine atom or afluorinated lower alkyl group, may be used. Specific examples includegroups in which one or more hydrogen atoms have been removed from amonocycloalkane such as cyclopentane or cyclohexane; and groups in whichone or more hydrogen atoms have been removed from a polycycloalkane suchas adamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Further, these groups in which one or more hydrogenatoms have been removed from a monocycloalkane and groups in which oneor more hydrogen atoms have been removed from a polycycloalkane may havepart of the carbon atoms constituting the ring replaced with an etherealoxygen atom (—O—).

Examples of acid dissociable, dissolution inhibiting groups containingan aliphatic cyclic group include (i) a group which has a tertiarycarbon atom on the ring structure of a monovalent aliphatic cyclicgroup; and (ii) a group which has a branched alkylene group containing atertiary carbon atom, and a monovalent aliphatic cyclic group to whichthe tertiary carbon atom is bonded.

Specific examples of (i) a group which has a tertiary carbon atom on thering structure of a monovalent aliphatic cyclic group include groupsrepresented by general formulas (1-1) to (1-9) shown below.

Specific examples of (ii) a group which has a branched alkylene groupcontaining a tertiary carbon atom, and a monovalent aliphatic cyclicgroup to which the tertiary carbon atom is bonded include groupsrepresented by general formulas (2-1) to (2-6) shown below.

In the formulas above, R¹⁴ represents an alkyl group; and g representsan integer of 0 to 8.

In the formulas above, each of R¹⁵ and R¹⁶ independently represents analkyl group.

As the alkyl group for R¹⁴, a linear or branched alkyl group ispreferable.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5. Specific examples of such branched alkyl groupsinclude an isopropyl group, an isobutyl group, a tert-butyl group, anisopentyl group and a neopentyl group, and an isopropyl group isparticularly desirable.

g is preferably an integer of 0 to 3, more preferably 1 to 3, and stillmore preferably 1 or 2.

As the alkyl group for R¹⁵ and R¹⁶, the same alkyl groups as those forR¹⁴ can be used.

In formulas (1-1) to (1-9) and (2-1) to (2-6), part of the carbon atomsconstituting the ring may be replaced with an ethereal oxygen atom(—O—).

Further, in formulas (1-1) to (1-9) and (2-1) to (2-6), one or more ofthe hydrogen atoms bonded to the carbon atoms constituting the ring maybe substituted with a substituent. Examples of substituents include alower alkyl group, a fluorine atom and a fluorinated alkyl group.

An “acetal-type acid dissociable, dissolution inhibiting group”generally substitutes a hydrogen atom at the terminal of analkali-soluble group such as a carboxy group or hydroxyl group, so as tobe bonded with an oxygen atom. When acid is generated upon exposure, thegenerated acid acts to break the bond between the acetal-type aciddissociable, dissolution inhibiting group and the oxygen atom to whichthe acetal-type, acid dissociable, dissolution inhibiting group isbonded.

Examples of acetal-type acid dissociable, dissolution inhibiting groupsinclude groups represented by general formula (p1) shown below.

In the formula, R¹′ and R²′ each independently represent a hydrogen atomor a lower alkyl group; n represents an integer of 0 to 3; and Yrepresents a lower alkyl group or an aliphatic cyclic group.

In general formula (p1) above, n is preferably an integer of 0 to 2,more preferably 0 or 1, and most preferably 0.

As the lower alkyl group for R¹′ and R²′, the same lower alkyl groups asthose described above for R¹ can be used, although a methyl group orethyl group is preferable, and a methyl group is particularly desirable.

In the present invention, it is preferable that at least one of R¹′ andR²′ be a hydrogen atom. That is, it is preferable that the aciddissociable, dissolution inhibiting group (p1) is a group represented bygeneral formula (p1-1) shown below.

In the formula, R¹′, n and Y are the same as defined above.

As the lower alkyl group for Y, the same as the lower alkyl groups forR¹ can be used.

As the aliphatic cyclic group for Y, any of the aliphaticmonocyclic/polycyclic groups which have been proposed for conventionalArF resists and the like can be appropriately selected for use. Forexample, the same groups described above in connection with the“aliphatic cyclic group” can be used.

Further, as the acetal-type, acid dissociable, dissolution inhibitinggroup, groups represented by general formula (p2) shown below can alsobe used.

In the formula, R¹⁷ and R¹⁸ each independently represent a linear orbranched alkyl group or a hydrogen atom; and R¹⁹ represents a linear,branched or cyclic alkyl group; or R¹⁷ and R¹⁹ each independentlyrepresents a linear or branched alkylene group, and the terminal of R¹⁷is bonded to the terminal of R¹⁹ to form a ring.

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is particularly desirable that either one of R¹⁷ and R¹⁸ be ahydrogen atom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferablyhas 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferablyan alkyl group of 1 to 5 carbon atoms, more preferably an ethyl group ormethyl group, and most preferably an ethyl group.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. As examples of the cycloalkyl group, groups in which oneor more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group, may be used. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane and cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

In general formula (p2) above, R¹⁷ and R¹⁹ may each independentlyrepresent a linear or branched alkylene group (preferably an alkylenegroup of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bonded tothe terminal of R¹⁷.

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atomhaving R¹⁹ bonded thereto, and the carbon atom having the oxygen atomand R¹⁷ bonded thereto. Such a cyclic group is preferably a 4 to7-membered ring, and more preferably a 4 to 6-membered ring. Specificexamples of the cyclic group include tetrahydropyranyl group andtetrahydrofuranyl group.

Specific examples of acetal-type acid dissociable, dissolutioninhibiting groups include groups represented by formulas (p3-1) to(p3-12) shown below.

In the formulas above, R¹³ represents a hydrogen atom or a methyl group;and g is the same as defined above.

Specific examples of the structural unit (a1) include a structural unitrepresented by general formula (a1-0-1) shown below and a structuralunit represented by general formula (a1-0-2) shown below.

In the formulas, R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; X¹ represents an acid dissociable,dissolution inhibiting group; Y² represents a divalent linking group;and X² represents an acid dissociable, dissolution inhibiting group.

In general formula (al-0-1), R is the same as defined for R¹ in formula(a0-1).

X¹ is not particularly limited as long as it is an acid dissociable,dissolution inhibiting group. Examples thereof include theaforementioned tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups and acetal-type acid dissociable, dissolutioninhibiting groups, and tertiary alkyl ester-type acid dissociable,dissolution inhibiting groups are preferable.

In general formula (a1-0-2), R is the same as defined above.

X² is the same as defined for X¹ in general formula (a1-0-1).

As examples of the divalent linking group for Y², the same groups asthose described above for R² in formula (a0-1) can be given.

As Y², the aforementioned alkylene group, a divalent aliphatic cyclicgroup or a divalent linking group containing a hetero atom ispreferable. Among these, a divalent linking group containing a heteroatom is preferable, and a linear group containing an oxygen atom as aheteratom, e.g., a group containing an ester bond is particularlydesirable.

More specifically, a group represented by the aforementioned formula-A-O—B— or -A—C(═O)—O—B— is preferable, and a group represented by theformula —(CH₂)_(a)—C(═O)—O—(CH₂)_(b)— is particularly desirable.

a represents an integer of 1 to 5, preferably 1 or 2, and mostpreferably 1.

b represents an integer of 1 to 5, preferably 1 or 2, and mostpreferably 1.

Specific examples of the structural unit (a1) include structural unitsrepresented by general formulas (a1-1) to (a1-4) shown below.

In the formulas, X′ represents a tertiary alkyl ester-type aciddissociable, dissolution inhibiting group; Y represents a lower alkylgroup of 1 to 5 carbon atoms or an aliphatic cyclic group; n representsan integer of 0 to 3; Y² represents a divalent linking group; R is thesame as defined above; and each of R¹′ and R²′ independently representsa hydrogen atom or a lower alkyl group of 1 to 5 carbon atoms.

Examples of the tertiary alkyl ester-type acid dissociable, dissolutioninhibiting group for X′ include the same tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups as those described above forX¹.

As R¹′, R²′, n and Y are respectively the same as defined for R¹′, R²′,n and Y in general formula (p1) described above in connection with the“acetal-type acid dissociable, dissolution inhibiting group”.

As examples of Y², the same groups as those described above for Y² ingeneral formula (a1-0-2) can be given.

Specific examples of structural units represented by general formula(a1-1) to (a1-4) are shown below.

In the formulas shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

As the structural unit (a1), one type of structural unit may be used, ortwo or more types may be used in combination.

In the present invention, in terms of achieving excellent lithographyproperties with respect to resolution, the shape of resist pattern andthe like, it is particularly desirable that the structural unit (a1)includes at least one structural unit selected from the group consistingof a structural unit represented by general formula (a1-0-11) shownbelow, a structural unit represented by general formula (a1-0-12) shownbelow and a structural unit represented by general formula (a1-0-2)shown below.

In the formulas, R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R²¹ represents an alkyl group; R²²represents a group which forms an aliphatic monocyclic group with thecarbon atoms to which R²² is bonded; R²³ represents a branched alkylgroup; R²⁴ represents a group which forms an aliphatic polycyclic groupwith the carbon atoms to which R²⁴ is bonded; Y² represents a divalentlinking group; and X² represents an acid dissociable, dissolutioninhibiting group.

In the formulas, R, Y² and X² are the same as defined above.

In general formula (a1-0-11), as the alkyl group for R²¹, the same alkylgroups as those described above for R¹⁴ in formulas (1-1) to (1-9) canbe used, preferably a methyl group or an ethyl group, and mostpreferably an ethyl group.

As the aliphatic monocyclic group formed by R²² and the carbon atoms towhich R²² is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociable,dissolution inhibiting group and which are monocyclic can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane. The monocycloalkane ispreferably a 3- to 11-membered ring, more preferably a 3- to 8-memberedring, still more preferably a 4- to 6-membered ring, and most preferablya 5- or 6-membered ring.

The monocycloalkane may or may not have part of the carbon atomsconstituting the ring replaced with an ethereal oxygen atom (—O—).

Further, the monocycloalkane may have a substituent such as a loweralkyl group, a fluorine atom or a fluorinated alkyl group.

As an examples of R²² constituting such an aliphatic cyclic group, analkylene group which may have an ethereal oxygen atom (—O—) interposedbetween the carbon atoms can be given.

Specific examples of structural units represented by general formula(a1-0-11) include structural units represented by the aforementionedformulas (a1-1-16) to (a1-1-23). Among these, a structural unitrepresented by general formula (a1-1-02) shown below which includes thestructural units represented by the aforementioned formulas (a1-1-16),(a1-1-17) and (a1-1-20) to (a1-1-23) is preferable. Further, astructural unit represented by general formula (a1-1-02′) shown below isalso preferable.

In the formulas shown below, h is preferably 1 or 2, and most preferably2.

In the formulas, R and R²¹ are the same as defined above; and hrepresents an integer of 1 to 3.

In general formula (a1-0-12), as the branched alkyl group for R²³, thesame alkyl groups as those described above for R¹⁴ which are branchedcan be used, and an isopropyl group is particularly desirable.

As the aliphatic polycyclic group formed by R²⁴ and the carbon atoms towhich R²⁴ is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociable,dissolution inhibiting group and which are polycyclic can be used.

Specific examples of structural units represented by general formula(a1-0-12) include structural units represented by the aforementionedformulas (a1-1-26) to (a1-1-31).

Examples of structural units represented by general formula (a1-0-2)include structural units represented by the aforementioned formulas(a1-3) and (a1-4).

As a structural unit represented by general formula (a1-0-2), those inwhich Y² is a group represented by the aforementioned formula -A-O—B— or-A-C(═O)—O—B— is particularly desirable.

Preferable examples of such structural units include a structural unitrepresented by general formula (a1-3-01) shown below, a structural unitrepresented by general formula (a1-3-02) shown below, and a structuralunit represented by general formula (a1-3-03) shown below.

In the formula, R and R″ are the same as defined above; R¹³ represents ahydrogen atom or a methyl group; and a represents an integer of 1 to 10.

In the formula, R and R¹⁴ are the same as defined above; R¹³ representsa hydrogen atom or a methyl group; a represents an integer of 1 to 10;and n′ represents an integer of 0 to 3.

In the formula, R is as defined above; each of Y²′ and Y²″ independentlyrepresents a divalent linking group; X′ represents an acid dissociable,dissolution inhibiting group; and n represents an integer of 1 to 3.

In general formulas (a1-3-01) and (a1-3-02), R¹³ is preferably ahydrogen atom.

a is preferably an integer of 1 to 8, more preferably 1 to 5, and mostpreferably 1 or 2.

n′ is preferably 1 or 2, and most preferably 2.

Specific examples of structural units represented by general formula(a1-3-01) include structural units represented by the aforementionedformulas (a1-3-25) and (a1-3-26).

Specific examples of structural units represented by general formula(a1-3-02) include structural units represented by the aforementionedformulas (a1-3-27) and (a1-3-28).

In general formula (a1-3-03), as the divalent linking group for Y²′ andY²″, the same groups as those described above for Y² in general formula(a1-3) can be used.

As Y²′, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As Y²″, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As the acid dissociable, dissolution inhibiting group for X′, the samegroups as those described above can be used. X′ is preferably a tertiaryalkyl ester-type acid dissociable, dissolution inhibiting group, morepreferably the aforementioned group (i) which has a tertiary carbon atomon the ring structure of a monovalent aliphatic cyclic group. Among theaforementioned groups (i), a group represented by general formula (1-1)above is preferable.

n represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

As the structural unit represented by general formula (a1-3-03), astructural unit represented by general formula (a1-3-03-1) or(a1-3-03-2) shown below is preferable. Among these, a structural unitrepresented by general formula (a1-3-03-1) is preferable, and astructural unit represented by the aforementioned formula (a1-3-29) or(a1-3-30) is particularly desirable.

In the formulas, R and R¹⁴ are the same as defined above; R²⁰ representsa hydrogen atom or a methyl group; a represents an integer of 1 to 10; brepresents an integer of 1 to 10; and t represents an integer of 0 to 3.

a is preferably an integer of 1 to 5, and most preferably 1 or 2.

b is preferably an integer of 1 to 5, and most preferably 1 or 2.

t is preferably an integer of 1 to 3, and most preferably 1 or 2.

In the present invention, it is particularly desirable to include atleast two types of structural units as the structural unit (a1).

In such a case, it is preferable that at least one of the at least twostructural units is a structural unit selected from the group consistingof a structural unit represented by general formula (a1-0-11), astructural unit represented by general formula (a1-0-12) and astructural unit represented by general formula (a1-0-2).

The structural unit (a1) including at least two types of structuralunits may consist of structural units selected from the group consistingof a structural unit represented by general formula (a1-0-11), astructural unit represented by general formula (a1-0-12) and astructural unit represented by general formula (a1-0-2). Alternatively,the structural unit (a1) may be a combination of at least one structuralunit selected from the aforementioned group and a structural unit whichdoes not fall under the category of the aforementioned group.

As examples of the structural unit which can be used in combination withat least one structural unit selected from the group consisting of astructural unit represented by general formula (a1-0-11), a structuralunit represented by general formula (a1-0-12) and a structural unitrepresented by general formula (a1-0-2) and does not fall under thecategory of the aforementioned group, a structural unit represented bygeneral formula (a1-1-10) shown below which includes the structuralunits represented by the aforementioned (al-1-1), (a1-1-2), (a1-1-7) to(a1-1-15) described above as specific examples of structural unitsrepresented by general formula (a1-1), structural units represented bygeneral formula (a1-2) and structural units represented by generalformula (a1-4) can be given.

As a structural unit represented by general formula (a1-1-10), astructural unit represented by general formula (a1-1-101) shown belowwhich includes the aforementioned formulas (a1-1-1) and (a1-1-2) isparticularly desirable.

In the formulas, R is the same as defined above; each of R²⁵ and R¹¹independently represents a linear alkyl group of 1 to 5 carbon atoms;and R²⁴ is the same as defined above.

In the component (A1) or (A1′), the amount of the structural unit (a1)based on the combined total of all structural units constituting thecomponent (A1) or (A1′) is preferably 10 to 80 mol %, more preferably 20to 70 mol %, and still more preferably 25 to 50 mol %. By ensuring thatthe amount of the structural unit (a1) is at least as large as the lowerlimit of the above-mentioned range, a pattern can be easily formed usinga resist composition prepared from the component (A1). On the otherhand, by ensuring that the amount of the structural unit (a1) is no morethan the upper limit of the above-mentioned range, a good balance can beachieved with the other structural units.

(Structural Unit (a2))

The structural unit (a2) is a structural unit derived from an acrylateester containing a lactone-containing cyclic group which does not fallunder the category of the aforementioned structural units (a0) and (a1).

The term “lactone-containing cyclic group” refers to a cyclic groupincluding one ring containing a —O—C(O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings.

When the component (A1) or (A1′) is used for forming a resist film, thelactone-containing cyclic group of the structural unit (a2) is effectivein improving the adhesion between the resist film and the substrate, andincreasing the compatibility with the developing solution containingwater.

As the structural unit (a2), there is no particular limitation, and anarbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include agroup in which one hydrogen atom has been removed from a 4- to6-membered lactone ring, such as a group in which one hydrogen atom hasbeen removed from β-propionolatone, a group in which one hydrogen atomhas been removed from γ-butyrolactone, and a group in which one hydrogenatom has been removed from δ-valerolactone. Further, specific examplesof lactone-containing polycyclic groups include groups in which onehydrogen atom has been removed from a lactone ring-containingbicycloalkane, tricycloalkane or tetracycloalkane.

More specifically, examples of the structural unit (a2) includestructural units represented by general formulas (a2-1) to (a2-5) shownbelow.

In the formula, R, R′ and A″ are the same as defined above; R²⁹represents a single bond or a divalent linking group; s″ represents aninteger of 0 to 2; and m represents 0 or 1.

R²⁹ represents a single bond or a divalent linking group Examples ofdivalent linking groups include the same divalent linking groups asthose described above for R². Among these, an alkylene group, an esterbond (—C(═O)—O—) or a combination thereof is preferable. The alkylenegroup as a divalent linking group for R²⁹ is preferably a linear orbranched alkylene group. Specific examples include the same linearalkylene groups and branched alkylene groups as those described abovefor R².

S″ is preferably 1 or 2.

Specific examples of structural units represented by general formulas(a2-1) to (a2-5) are shown below. In the formulas shown below, R^(α)represents a hydrogen atom, a methyl group or a trifluoromethyl group.

In the component (A1) or (A1′), as the structural unit (a2), one type ofstructural unit may be used, or two or more types may be used incombination.

In the present invention, when the component (A) includes the component(A1), it is particularly desirable that the component (A1) contain, as astructural unit (a2), at least one structural unit selected from thegroup consisting of a structural unit represented by general formula(a2-1) and a structural unit represented by general formula (a2-2).

When the component (A) includes the component (A1), in terms ofimproving the adhesion between a substrate and a resist film formedusing a positive resist composition containing the component (A1) andincreasing the compatibility with a developing solution, the amount ofthe structural unit (a2) within the component (A1), based on thecombined total of all structural units constituting the component (A1)is preferably 1 to 50 mol %, more preferably 5 to 50 mol %, and stillmore preferably 10 to 45 mol %.

Further, in terms of achieving excellent lithography properties, theamount of the structural unit (a0) and the structural unit (a2) (theamount of the structural unit (a0) when the component (A1) contains nostructural unit (a2)) within the component (A1), based on the combinedtotal of all structural units constituting the component (A1) ispreferably 5 to 70 mol %, more preferably 1 to 70 mol %, still morepreferably 10 to 65 mol %, and most preferably 20 to 65 mol %. Byensuring the above-mentioned range, MEF, CDU and the pattern shape canbe further improved.

When the component (A1) contains both of the structural unit (a0) andthe structural unit (a2), the amount of the structural unit (a0) withinthe component (A1), based on the combined total of all structural unitsconstituting the component (A1) is preferably 1 to 40 mol %, morepreferably 10 to 35 mol %, and most preferably 15 to 30 mol %; and theamount of the structural unit (a2) within the component (A1), based onthe combined total of all structural units constituting the component(A1) is preferably 1 to 45 mol %, more preferably 10 to 45 mol %, andmost preferably 20 to 45 mol %.

On the other hand, when the component (A) includes the component (A1′),in terms of improving the adhesion between a substrate and a resist filmformed using a positive resist composition containing the component(A1′) and increasing the compatibility with a developing solution, theamount of the structural unit (a2) within the component (A1′), based onthe combined total of all structural units constituting the component(A1′) is preferably 5 to 70 mol %, more preferably 10 to 65 mol %, stillmore preferably 20 to 65 mol %, and most preferably 20 to 45 mol %. Byensuring the above-mentioned range, MEF, CDU and the pattern shape canbe further improved.

Further, in terms of achieving excellent lithography properties, theamount of the structural unit (a0) and the structural unit (a2) withinthe component (A1′), based on the combined total of all structural unitsconstituting the component (A1′) is preferably 5 to 70 mol %, morepreferably 1 to 70 mol %, still more preferably 10 to 65 mol %, and mostpreferably 20 to 65 mol %. By ensuring the above-mentioned range, MEF,CDU and the pattern shape can be further improved.

The component (A1′) includes an acid dissociable, dissolution inhibitinggroup within the structure thereof.

The acid dissociable, dissolution inhibiting group is a group having analkali dissolution-inhibiting effect that renders the entire component(A1′) insoluble in an alkali developing solution prior to dissociation,and is dissociated from the component (A1′) by the action of acidgenerated from the component (B) upon exposure. Therefore, when the aciddissociable, dissolution inhibiting group is dissociated from thecomponent (A1′), the solubility of the entire component (A1′) in analkali developing solution is increased.

The acid dissociable, dissolution inhibiting group can be incorporatedinto the component (A1′) by using a structural unit (a0) and/or astructural unit (a2) that contains an acid dissociable, dissolutioninhibiting group within the structure thereof, or by using a structuralunit other than the structural units (a0) and (a2) that contains an aciddissociable, dissolution inhibiting group.

For example, the structural units represented by formulas (a2-1-5) to(a2-1-7), (a2-2-10) and (a2-2-11) described above for the structuralunit (a2) contain a lactone-containing cyclic group that functions as anacid dissociable, dissolution inhibiting group.

Further, among the structural units described above for the structuralunit (a0), with respect to a structural unit in which a tertiary carbonatom is bonded to the terminal oxygen atom of the carbonyloxy group(—C(O)—O—) bonded to the cyclic group in formula (a0-1) (e.g., astructural unit in which R′ represents an alkyl group, and the cyclicgroup in formula (a0-1) represents an acid dissociable, dissolutioninhibiting group, as in the case of the structural unit (a2) describedabove), the cyclic group also functions as an acid dissociable,dissolution inhibiting group. Furthermore, in a structural unit (a0) inwhich R² has an acid dissociable portion within the structure thereof,the portion from the acid dissociable portion to the terminal functionsas an acid dissociable, dissolution inhibiting group.

When such a structural unit containing an acid dissociable, dissolutioninhibiting group-equivalent group/portion within the structure thereofis used as the structural unit (a0) and/or structural unit (a2), thecomponent (A1′) may consist of the structural units (a0) and (a2), ormay further contain an optional structural unit (e.g., theaforementioned structural unit (a1), or the structural unit (a3) or (a4)described later).

On the other hand, when a structural unit containing no aciddissociable, dissolution inhibiting group-equivalent group/portionwithin the structure thereof is used as the structural unit (a0) and/orstructural unit (a2), it is necessary that the component (A1′) contain astructural unit having an acid dissociable, dissolution inhibiting group(e.g., the aforementioned structural unit (a1), the below-describedstructural unit (a3), the below-described structural unit (A4), or thelike) in addition to the structural units (a0) and (a2).

In the present invention, as a structural unit having an aciddissociable, dissolution inhibiting group, it is preferable to containthe aforementioned structural unit (a1).

(Structural Unit (a3))

The structural unit (a3) is a structural unit derived from an acrylateester containing a polar group-containing aliphatic hydrocarbon group.

When the component (A1) or (A1′) includes the structural unit (a3), thehydrophilicity of the component (A) is improved, and hence, thecompatibility of the component (A) with the developing solution isimproved. As a result, the alkali solubility of the exposed portionsimproves, which contributes to favorable improvements in the resolution.

Examples of the polar group include a hydroxyl group, a cyano group, acarboxyl group, or a fluorinated alcohol group (a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms), although a hydroxyl group isparticularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (and preferably alkylene groups) of 1 to 10 carbonatoms, and polycyclic aliphatic hydrocarbon groups (polycyclic groups).These polycyclic groups can be selected appropriately from the multitudeof groups that have been proposed for the resins of resist compositionsdesigned for use with ArF excimer lasers. The polycyclic grouppreferably has 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, a cyano group, a carboxyl group or a fluorinated alcoholgroup are particularly desirable. Examples of polycyclic groups includegroups in which two or more hydrogen atoms have been removed from abicycloalkane, tricycloalkane, tetracycloalkane or the like. Specificexamples include groups in which two or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane. Of these polycyclicgroups, groups in which two or more hydrogen atoms have been removedfrom adamantane, norbornane or tetracyclododecane are preferredindustrially.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulas, R is as defined above; j is an integer of 1 to 3; k isan integer of 1 to 3; t′ is an integer of 1 to 3;1 is an integer of 1 to5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. 1 is preferably 1. s ispreferably 1. Further, in formula (a3-3), it is preferable that a2-norbornyl group or 3-norbornyl group be bonded to the terminal of thecarboxy group of the acrylic acid. The fluorinated alkyl alcohol ispreferably bonded to the 5th or 6th position of the norbornyl group.

As the structural unit (a3), one type of structural unit may be used, ortwo or more types may be used in combination.

The amount of the structural unit (a3) based on the combined total ofall structural units constituting the component (A1) or (A1′) ispreferably 5 to 50 mol %, more preferably 5 to 40 mol %, still morepreferably 5 to 25 mol %, and most preferably 5 to 15 mol %.

(Other Structural Units)

The component (A1) or (A1′) may also have a structural unit (a4) whichis other than the above-mentioned structural units (a0) to (a3), as longas the effects of the present invention are not impaired.

As the structural unit (a4), any other structural unit which cannot beclassified as one of the above structural units (a0) to (a3) can be usedwithout any particular limitation, and any of the multitude ofconventional structural units used within resist resins for ArF excimerlasers or KrF excimer lasers (and particularly for ArF excimer lasers)can be used.

As the structural unit (a4), a structural unit which contains anon-acid-dissociable aliphatic polycyclic group, and is also derivedfrom an acrylate ester is preferable. Examples of this polycyclic groupinclude the same groups as those described above in connection with theaforementioned structural unit (a1), and any of the multitude ofconventional polycyclic groups used within the resin component of resistcompositions for ArF excimer lasers or KrF excimer lasers (andparticularly for ArF excimer lasers) can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecanyl group,adamantyl group, tetracyclododecanyl group, isobornyl group, andnorbornyl group is particularly desirable. These polycyclic groups maybe substituted with a linear or branched alkyl group of 1 to 5 carbonatoms.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a4-1) to (a4-5) shown below.

In the formulas, R is the same as defined above.

When the structural unit (a4) is included in the component (A1) or(A1′), the amount of the structural unit (a4) based on the combinedtotal of all the structural units that constitute the component (A1) or(A1′) is preferably within the range from 1 to 30 mol %, and morepreferably from 10 to 20 mol %.

The component (A1) is preferably a copolymer containing the structuralunits (a0) and (a1). Examples of such copolymers include a copolymerconsisting of the structural units (a0) and (a1), a copolymer consistingof the structural units (a0), (a1) and (a3), a copolymer consisting ofthe structural units (a0), (a1) and (a2), and a copolymer consisting ofthe structural units (a0), (a1), (a2) and (a3).

The component (A1′) is preferably a copolymer containing the structuralunits (a0) and (a2), and more preferably a copolymer containing thestructural units (a0), (a1) and (a2). Examples of such copolymersinclude a copolymer consisting of the structural units (a0) and (a2), acopolymer consisting of the structural units (a0), (a1) and (a2), and acopolymer consisting of the structural units (a0), (a1), (a2) and (a3).However, in the case of a copolymer consisting of the structural units(a0) and (a2), it is necessary that either or both of the structuralunits (a0) and (a2) contain an acid dissociable, dissolution inhibitinggroup.

In the present invention, it is particularly desirable that such acopolymer contains, as the structural unit (a1), at least one memberselected from the group consisting of a structural unit represented bygeneral formula (a1-0-11), a structural unit represented by generalformula (a1-0-12), and a structural unit represented by general formula(a1-0-2).

Further, as described above, such a copolymer preferably contains atleast two types of structural units as the structural unit (a1), and itis particularly desirable that at least one of the at least twostructural units is selected from the group consisting of a structuralunit represented by general formula (a1-0-11), a structural unitrepresented by general formula (a1-0-12), and a structural unitrepresented by general formula (a1-0-2).

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (A1)or (A1′) is not particularly limited, but is preferably 2,000 to 50,000,more preferably 3,000 to 30,000, and most preferably 5,000 to 20,000. Byensuring that the weight average molecular weight is no more than theupper limit of the above-mentioned range, the polymeric compound (A1)exhibits satisfactory solubility in a resist solvent when used as aresist. On the other hand, by ensuring that the weight average molecularweight is at least as large as the lower limit of the above-mentionedrange, dry etching resistance and cross-sectional shape of the resistpattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, morepreferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is thenumber average molecular weight.

In the component (A), as the component (A1) or (A1′), one type may beused, or two or more types of compounds may be used in combination.

In the component (A), the amount of the component (A1) or (A1′) based onthe total weight of the component (A) is preferably 25% by weight ormore, more preferably 50% by weight or more, still more preferably 75%by weight or more, and may be even 100% by weight. When the amount ofthe component (A1) is 25% by weight or more, various lithographyproperties are improved.

The component (A1) or (A1′) can be obtained, for example, by aconventional radical polymerization or the like of the monomerscorresponding with each of the structural units, using a radicalpolymerization initiator such as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A1) or (A1′), by using a chain transferagent such as HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can beintroduced at the terminals of the component (A1) or (A1′). Such acopolymer having introduced a hydroxyalkyl group in which some of thehydrogen atoms of the alkyl group are substituted with fluorine atoms iseffective in reducing developing defects and LER (line edge roughness:unevenness of the side walls of a line pattern).

As the monomers for deriving the corresponding structural units,commercially available monomers may be used, or the monomers may besynthesized by a conventional method.

For example, as a monomer for deriving the structural unit (a0), acompound (I) represented by general formula (I) shown below can be used.

In general formula (I), R¹, R², R′ and A″ are the same as defined above.

The method for producing the compound (I) is not particularly limited,and the compound (I) can be produced by a conventional method.

For example, in the presence of a base, a compound (X-2) represented bygeneral formula (X-2) shown below is added to a solution obtained bydissolving a compound (X-1) represented by general formula (X-1) shownbelow in a reaction solvent, and a reaction is effected to therebyobtain a compound (I).

Examples of the base include inorganic bases such as sodium hydride,K₂CO₃ and Cs₂CO₃; and organic bases such as triethylamine,4-dimethylaminopyridine (DMAP) and pyridine. Examples of condensingagents include carbodiimide reagents such asethyldiisopropylaminocarbodiimide hydrochloride (EDCI),dicyclohexylcarboxyimide (DCC), diisopropylcarbodiimide andcarbodiimidazole; tetraethyl pyrophosphate; andbenzotriazole-N-hydroxytrisdimethylaminophosphonium hexafluorophosphide(Bop reagent).

If desired, an acid may be used. As the acid, any acid generally usedfor dehydration/condensation may be used. Specific examples includeinorganic acids such as hydrochloric acid, sulfuric acid and phosphoricacid; and organic acids such as methanesulfonic acid,trifluoromethanesulfonic acid, benzenesulfonic acid andp-toluenesulfonic acid. These acids can be used individually, or in acombination of two or more.

In general formula (I), R¹, R², R′ and A″ are the same as defined above.

In the resist composition of the present invention, the component (A)may contain “a base component which exhibits increased solubility in analkali developing solution under action of acid” other than thecomponent (A1) and (A1′) (hereafter, referred to as “component (A2)”).

The component (A2) is not particularly limited, and any of the multitudeof conventional base components used within chemically amplified resistcompositions (e.g., base resins used within chemically amplified resistcompositions for ArF excimer lasers or KrF excimer lasers, preferablyArF excimer lasers) can be used. For example, as a base resin for ArFexcimer laser, a base resin having the aforementioned structural unit(a1) as an essential component, and optionally the aforementionedstructural units (a2) to (a4) can be used.

As the component (A2), one type of resin may be used, or two or moretypes of resins may be used in combination.

In the resist composition of the present invention, the amount of thecomponent (A) can be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

<Component (B)>

As the component (B), there is no particular limitation, and any of theknown acid generators used in conventional chemically amplified resistcompositions can be used. Examples of these acid generators arenumerous, and include onium salt acid generators such as iodonium saltsand sulfonium salts; oxime sulfonate acid generators; diazomethane acidgenerators such as bisalkyl or bisaryl sulfonyl diazomethanes andpoly(bis-sulfonyl)diazomethanes; nitrobenzylsulfonate acid generators;iminosulfonate acid generators; and disulfone acid generators.

As an onium salt acid generator, a compound represented by generalformula (b-1) or (b-2) shown below can be used.

In the formulas above, R″ to R³″, R⁵″ and R⁶″ each independentlyrepresent an aryl group or alkyl group, wherein two of R″ to R³″ may bebonded to each other to form a ring with the sulfur atom; and R⁴″represents an alkyl group, a halogenated alkyl group, an aryl group oran alkenyl group which may have a substituent, with the provision thatat least one of R¹″ to R³″ represents an aryl group, and at least one ofR⁵″ and R⁶″ represents an aryl group.

In formula (b-1), R¹″ to R³″ each independently represents an aryl groupor an alkyl group. In formula (b-1), two of R¹″ to R³″ may be bonded toeach other to form a ring with the sulfur atom.

Further, among R¹″ to R³″, at least one group represents an aryl group.Among R¹″ to R³″, two or more groups are preferably aryl groups, and itis particularly desirable that all of R¹″ to R³″ are aryl groups.

The aryl group for R¹″ to R³″ is not particularly limited. For example,an aryl group having 6 to 20 carbon atoms may be used in which part orall of the hydrogen atoms of the aryl group may or may not besubstituted with alkyl groups, alkoxy groups, halogen atoms or hydroxylgroups.

The aryl group is preferably an aryl group having 6 to 10 carbon atomsbecause it can be synthesized at a low cost. Specific examples thereofinclude a phenyl group and a naphthyl group.

The alkyl group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkyl group having 1 to 5 carbon atoms,and most preferably a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group.

The alkoxy group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkoxy group having 1 to 5 carbon atoms,more preferably a methoxy group, an ethoxy group, an n-propoxy group, aniso-propoxy group, an n-butoxy group or a tert-butoxy group, and mostpreferably a methoxy group or an ethoxy group.

The halogen atom, with which hydrogen atoms of the aryl group may besubstituted, is preferably a fluorine atom.

The alkyl group for R¹″ to R³″ is not particularly limited and includes,for example, a linear, branched or cyclic alkyl group having 1 to 10carbon atoms. In terms of achieving excellent resolution, the alkylgroup preferably has 1 to 5 carbon atoms.

Specific examples thereof include a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, an isobutyl group,an n-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexylgroup, a nonyl group, and a decanyl group, and a methyl group is mostpreferable because it is excellent in resolution and can be synthesizedat a low cost.

When two of R¹″ to R³″ in formula (b-1) are bonded to each other to forma ring with the sulfur atom, it is preferable that the two of R¹″ to R³″form a 3 to 10-membered ring including the sulfur atom, and it isparticularly desirable that the two of R¹″ to R³″ form a 5 to 7-memberedring including the sulfur atom.

When two of R¹″ to R³″ in formula (b-1) are bonded to each other to forma ring with the sulfur atom, the remaining one of R¹″ to R³″ ispreferably an aryl group. As examples of the aryl group, the same as theabove-mentioned aryl groups for R¹″ to R³″ can be given.

As preferable examples of the cation moiety for the compound representedby general formula (b-1), those represented by formulas (I-1-1) to(I-1-13), (I-2-1) and (I-2-2) shown below can be given. Among these, acation moiety having a triphenylmethane skeleton, such as a cationmoiety represented by any one of formulas (I-1-1) to (I-1-13) shownbelow is particularly desirable. Further, a group in which part or allof the phenyl groups within the cation moiety having a triphenylmethaneskeleton have been replaced with a naphthyl group which may have asubstituent can also be given as a preferable example.

In formulas (I-2-1) and (I-2-2), each of R⁹ and R¹⁰ independentlyrepresents a phenyl group or naphthyl group which may have asubstituent, an alkyl group of 1 to 5 carbon atoms, an alkoxy group or ahydroxy group.

u is an integer of 1 to 3, and most preferably 1 or 2.

R⁴″ represents an alkyl group, a halogenated alkyl group, an aryl groupor an alkenyl group which may have a substituent.

The alkyl group for R⁴″ may be any of linear, branched or cyclic.

The linear or branched alkyl group preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbonatoms.

The cyclic alkyl group preferably has 4 to 15 carbon atoms, morepreferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbonatoms.

As an example of the halogenated alkyl group for R⁴″, a group in whichpart of or all of the hydrogen atoms of the aforementioned linear,branched or cyclic alkyl group have been substituted with halogen atomscan be given. Examples of the aforementioned halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is preferable.

In the halogenated alkyl group, the percentage of the number of halogenatoms based on the total number of halogen atoms and hydrogen atoms(halogenation ratio (%)) is preferably 10 to 100%, more preferably 50 to100%, and most preferably 100%. Higher halogenation ratio is preferablebecause the acid strength increases.

The aryl group for R⁴″ is preferably an aryl group of 6 to 20 carbonatoms.

The alkenyl group for R⁴″ is preferably an alkenyl group of 2 to 10carbon atoms.

With respect to R⁴″, the expression “may have a substituent” means thatpart of or all of the hydrogen atoms within the aforementioned linear,branched or cyclic alkyl group, halogenated alkyl group, aryl group oralkenyl group may be substituted with substituents (atoms other thanhydrogen atoms, or groups).

R⁴″ may have one substituent, or two or more substituents.

Examples of the substituent include a halogen atom, a hetero atom, analkyl group which may have a substituent, and a group represented by theformula X-Q¹- (in the formula, Q¹ represents a divalent linking groupcontaining an oxygen atom; and X represents a hydrocarbon group of 3 to30 carbon atoms which may have a substituent).

Examples of the halogen atom as the substituent for R⁴″ include the samehalogen atoms as those described above with respect to the halogenatedalkyl group for R⁴″.

Examples of hetero atoms include an oxygen atom, a nitrogen atom, and asulfur atom.

Examples of the alkyl group as the substituent for R⁴″ include the samealkyl groups as those described above for the aforementioned “alkylgroup which may have a substituent”.

In the group represented by formula X-Q¹-, Q¹ represents a divalentlinking group containing an oxygen atom.

Q¹ may contain an atom other than an oxygen atom. Examples of atomsother than an oxygen atom include a carbon atom, a hydrogen atom, asulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an amido bond(—C(═O)—NH—), a carbonyl group (—C(═O)—) and a carbonate group(—O—C(═O)—O—); and combinations of the aforementioned non-hydrocarbon,hetero atom-containing linking groups with an alkylene group.

Specific examples of the combinations of the aforementionednon-hydrocarbon, hetero atom-containing linking groups and an alkylenegroup include —R⁹¹—O—, —R⁹²—O—C(═O)—, —C(═O)—O—R⁹³— and—C(═O)—O—R⁹³—O—C(═O)— (in the formulas, each of R⁹¹ to R⁹³ independentlyrepresents an alkylene group).

The alkylene group for R⁹¹ to R⁹³ is preferably a linear or branchedalkylene group, and preferably has 1 to 12 carbon atoms, more preferably1 to 5, and most preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—];alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—,—C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylenegroup [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—, and—C(CH₂CH₃)₂—CH₂—; a trimethylene group (n-propylene group)[—CH₂CH₂CH₂—]; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂— and—CH₂CH(CH₃)CH₂—; a tetramethylene group [—CH₂CH₂CH₂CH₂—];alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂— and—CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

Q¹ is preferably a divalent linking group containing an ester linkage orether linkage, and more preferably a group of —R⁹¹—O—, —R⁹²—O—C(═O)—,—C(═O)—O—, —C(═O)—O—R⁹³—, or —C(═O)—O—R⁹³—O—C(═O)—.

In the group represented by the formula X-Q¹-, the hydrocarbon group forX may be either an aromatic hydrocarbon group or an aliphatichydrocarbon group.

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring. The aromatic hydrocarbon ring preferably has 3 to 30 carbon atoms,more preferably 5 to 30, still more preferably 5 to 20, still morepreferably 6 to 15, and most preferably 6 to 12. Here, the number ofcarbon atoms within a substituent(s) is not included in the number ofcarbon atoms of the aromatic hydrocarbon group.

Specific examples of aromatic hydrocarbon groups include an aryl groupwhich is an aromatic hydrocarbon ring having one hydrogen atom removedtherefrom, such as a phenyl group, a biphenyl group, a fluorenyl group,a naphthyl group, an anthryl group or a phenanthryl group; and analkylaryl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group. The alkyl chain within the arylalkylgroup preferably has 1 to 4 carbon atom, more preferably 1 or 2, andmost preferably 1.

The aromatic hydrocarbon group may have a substituent. For example, partof the carbon atoms constituting the aromatic ring within the aromatichydrocarbon group may be substituted with a hetero atom, or a hydrogenatom bonded to the aromatic ring within the aromatic hydrocarbon groupmay be substituted with a substituent.

In the former example, a heteroaryl group in which part of the carbonatoms constituting the ring within the aforementioned aryl group hasbeen substituted with a hetero atom such as an oxygen atom, a sulfuratom or a nitrogen atom, and a heteroarylalkyl group in which part ofthe carbon atoms constituting the aromatic hydrocarbon ring within theaforementioned arylalkyl group has been substituted with theaforementioned heteroatom can be used.

In the latter example, as the substituent for the aromatic hydrocarbongroup, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) or the like can beused.

The alkyl group as the substituent for the aromatic hydrocarbon group ispreferably an alkyl group of 1 to 5 carbon atoms, and a methyl group, anethyl group, a propyl group, an n-butyl group or a tert-butyl group isparticularly desirable.

The alkoxy group as the substituent for the aromatic hydrocarbon groupis preferably an alkoxy group having 1 to 5 carbon atoms, morepreferably a methoxy group, ethoxy group, n-propoxy group, iso-propoxygroup, n-butoxy group or tert-butoxy group, and most preferably amethoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Example of the halogenated alkyl group as the substituent for thearomatic hydrocarbon group includes a group in which part or all of thehydrogen atoms within the aforementioned alkyl group have beensubstituted with the aforementioned halogen atoms.

The aliphatic hydrocarbon group for X may be either a saturatedaliphatic hydrocarbon group, or an unsaturated aliphatic hydrocarbongroup. Further, the aliphatic hydrocarbon group may be linear, branchedor cyclic.

In the aliphatic hydrocarbon group for X, a part of the carbon atomsconstituting the aliphatic hydrocarbon group may be substituted with asubstituent group containing a hetero atom, or a part or all of thehydrogen atoms constituting the aliphatic hydrocarbon group may besubstituted with a substituent group containing a hetero atom.

As the “hetero atom” for X, there is no particular limitation as long asit is an atom other than a carbon atom and a hydrogen atom. Examples ofhetero atoms include a halogen atom, an oxygen atom, a sulfur atom and anitrogen atom. Examples of halogen atoms include a fluorine atom, achlorine atom, an iodine atom and a bromine atom.

The substituent group containing a hetero atom may consist of a heteroatom, or may be a group containing a group or atom other than a heteroatom.

Specific examples of the substituent group for substituting part of thecarbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NH— (the H may be replaced with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. When the aliphatichydrocarbon group is cyclic, the aliphatic hydrocarbon group may containany of these substituent groups in the ring structure.

Examples of the substituent group for substituting part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the aforementioned halogenated alkyl group includes a groupin which part or all of the hydrogen atoms within an alkyl group of 1 to5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

As the aliphatic hydrocarbon group, a linear or branched saturatedhydrocarbon group, a linear or branched monovalent unsaturatedhydrocarbon group, or a cyclic aliphatic hydrocarbon group (aliphaticcyclic group) is preferable.

The linear saturated hydrocarbon group (alkyl group) preferably has 1 to20 carbon atoms, more preferably 1 to 15, and most preferably 1 to 10.Specific examples include a methyl group, an ethyl group, a propylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group, anoctyl group, a nonyl group, a decanyl group, an undecyl group, a dodecylgroup, a tridecyl group, an isotridecyl group, a tetradecyl group, apentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecylgroup, an octadecyl group, a nonadecyl group, an icosyl group, ahenicosyl group and a docosyl group.

The branched saturated hydrocarbon group (alkyl group) preferably has 3to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to10. Specific examples include a 1-methylethyl group, a 1-methylpropylgroup, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutylgroup, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutylgroup, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentylgroup and a 4-methylpentyl group.

The unsaturated hydrocarbon group preferably has 2 to 10 carbon atoms,more preferably 2 to 5, still more preferably 2 to 4, and mostpreferably 3. Examples of linear monovalent unsaturated hydrocarbongroups include a vinyl group, a propenyl group (an allyl group) and abutynyl group. Examples of branched monovalent unsaturated hydrocarbongroups include a 1-methylpropenyl group and a 2-methylpropenyl group.

Among the above-mentioned examples, as the unsaturated hydrocarbongroup, a propenyl group is particularly desirable.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group. The aliphatic cyclic group preferably has 3 to 30carbon atoms, more preferably 5 to 30, still more preferably 5 to 20,still more preferably 6 to 15, and most preferably 6 to 12.

As the aliphatic cyclic group, a group in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

When the aliphatic cyclic group does not contain a heteroatom-containing substituent group in the ring structure thereof, thealiphatic cyclic group is preferably a polycyclic group, more preferablya group in which one or more hydrogen atoms have been removed from apolycycloalkane, and a group in which one or more hydrogen atoms havebeen removed from adamantane is particularly desirable.

When the aliphatic cyclic group contains a hetero atom-containingsubstituent group in the ring structure thereof, the heteroatom-containing substituent group is preferably —O—, —C(═O)—O—, —S—,—S(═O)₂— or —S(═O)₂—O—. Specific examples of such aliphatic cyclicgroups include groups represented by formulas (L1) to (L5) and (S1) to(S4) shown below.

In the formula, Q″ represents an alkylene group of 1 to 5 carbon atoms,—O—, —S—, —O—R⁹⁴— or —S—R⁹⁵— (wherein each of R⁹⁴ and R⁹⁵ independentlyrepresents an alkylene group of 1 to 5 carbon atoms); and m represents 0or 1.

As the alkylene group for Q″, R⁹⁴ and R⁹⁵, the same alkylene groups asthose described above for R⁹¹ to R⁹³ can be used.

In these aliphatic cyclic groups, part of the hydrogen atoms boned tothe carbon atoms constituting the ring structure may be substituted witha substituent. Examples of substituents include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and an oxygen atom (═O).

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable,and a methyl group, an ethyl group, a propyl group, an n-butyl group ora tert-butyl group is particularly desirable.

As the alkoxy group and the halogen atom, the same groups as thesubstituent groups for substituting part or all of the hydrogen atomscan be used.

In the present invention, as X, a cyclic group which may have asubstituent is preferable. The cyclic group may be either an aromatichydrocarbon group which may have a substituent, or an aliphatic cyclicgroup which may have a substituent, and an aliphatic cyclic group whichmay have a substituent is preferable.

As the aromatic hydrocarbon group, a naphthyl group which may have asubstituent, or a phenyl group which may have a substituent ispreferable.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, and groupsrepresented by formulas (L2) to (L5), (S3) and (S4) are preferable.

In the present invention, R⁴″ preferably has X-Q¹- as a substituent. Insuch a case, R⁴″ is preferably a group represented by the formulaX-Q¹-Y¹— (in the formula, Q¹ and X are the same as defined above; and Y¹represents an alkylene group of 1 to 4 carbon atoms which may have asubstituent, or a fluorinated alkylene group of 1 to 4 carbon atomswhich may have a substituent).

In the group represented by the formula X-Q¹-Y¹—, as the alkylene groupfor Y¹, the same alkylene group as those described above for Q¹ in whichthe number of carbon atoms is 1 to 4 can be used.

As the fluorinated alkylene group, the aforementioned alkylene group inwhich part or all of the hydrogen atoms has been substituted withfluorine atoms can be used,

Specific examples of Y¹ include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—,—CF(CF₃)CF₂—, —CF(CF₂CF₃)—, —C(CF₃)₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—,—CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—,—CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—, —CH₂CF₂—, —CH₂CH₂CF₂—,—CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—, —C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—,—CH₂CH₂CF₂CF₂—, —CH(CF₃)CH₂CH₂—, —CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—,—C(CF₃)₂CH₂—; —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and—C(CH₃)(CH₂CH₃)—.

Y¹ is preferably a fluorinated alkylene group, and particularlypreferably a fluorinated alkylene group in which the carbon atom bondedto the adjacent sulfur atom is fluorinated. Examples of such fluorinatedalkylene groups include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—,—CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—,—C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—; —CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—;—CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and —CH₂CF₂CF₂CF₂—.

Of these, —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂— or CH₂CF₂CF₂— is preferable,—CF₂—, —CF₂CF₂— or —CF₂CF₂CF₂— is more preferable, and —CF₂— isparticularly desirable.

The alkylene group or fluorinated alkylene group may have a substituent.The alkylene group or fluorinated alkylene group “has a substituent”means that part or all of the hydrogen atoms or fluorine atoms in thealkylene group or fluorinated alkylene group has been substituted withgroups other than hydrogen atoms and fluorine atoms.

Examples of substituents which the alkylene group or fluorinatedalkylene group may have include an alkyl group of 1 to 4 carbon atoms,an alkoxy group of 1 to 4 carbon atoms, and a hydroxyl group.

In formula (b-2), R⁵″ and R⁶″ each independently represent an aryl groupor alkyl group. At least one of R⁵″ and R⁶″ represents an aryl group. Itis preferable that both of R⁵″ and R⁶″ represent an aryl group.

As the aryl group for R⁵″ and R⁶″, the same as the aryl groups for R¹″to R³″ can be used.

As the alkyl group for R⁵″ and R⁶″, the same as the alkyl groups for R¹″to R³″ can be used.

It is particularly desirable that both of R⁵″ and R⁶″ represents aphenyl group.

As R⁴″ in formula (b-2), the same groups as those mentioned above forR⁴″ in formula (b-1) can be used.

Specific examples of suitable onium salt acid generators represented byformula (b-1) or (b-2) include diphenyliodoniumtrifluoromethanesulfonate or nonafluorobutanesulfonate;bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate ornonafluorobutanesulfonate; triphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-methylphenyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;monophenyldimethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenylmonomethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;di(1-naphthyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-phenyltetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(4-methylphenyl)tetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyptetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-methoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-ethoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-phenyltetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-(4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyptetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; and 1-(4-methylphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate.

It is also possible to use onium salts in which the anion moiety ofthese onium salts are replaced by an alkylsulfonate which may have asubstituent, such as methanesulfonate, n-propanesulfonate,n-butanesulfonate, n-octanesulfonate, 1-adamantanesulfonate,2-norbornanesulfonate, or d-camphor-10-sulfonate.

Furthermore, onium salts in which the anion moiety of these onium saltsare replaced by an anion moiety represented by any one of formulas (1)to (b8) shown below can be used.

In the formulas, p represents an integer of 1 to 3; each of q1 and q2independently represents an integer of 1 to 5; q3 represents an integerof 1 to 12; each of r1 and r2 independently represents an integer of 0to 3; g represents an integer of 1 to 20; t3 represents an integer of 1to 3; and R⁷ represents a substituent.

In the formulas, p, R⁷ and Q″ are the same as defined above; each of n1to n5 independently represents 0 or 1; each of v1 to v5 independentlyrepresents an integer of 0 to 3; and each of w1 to w5 independentlyrepresents an integer of 0 to 3.

As the substituent for R⁷, the same groups as those which theaforementioned aliphatic hydrocarbon group or aromatic hydrocarbon groupfor X may have as a substituent can be used.

If there are two or more of the R⁷ group, as indicated by the values r1,r2, and w1 to w5, then the two or more of the R⁷ groups may be the sameor different from each other.

Each of r1, r2, and w1 to w5 is preferably an integer of 0 to 2, andmore preferably 0 or 1.

t3 is preferably 1 or 2, and most preferably 1.

q3 is preferably 1 to 5, more preferably 1 to 3, and most preferably 1.

Further, onium salt-based acid generators in which the anion moiety ingeneral formula (b-1) or (b-2) is replaced by an anion moietyrepresented by general formula (b-3) or (b-4) shown below (the cationmoiety is the same as (b-1) or (b-2)) may be used.

In formulas (b-3) and (b-4) above, X″ represents an alkylene group of 2to 6 carbon atoms in which at least one hydrogen atom has beensubstituted with a fluorine atom; and each of Y″ and Z″ independentlyrepresents an alkyl group of 1 to 10 carbon atoms in which at least onehydrogen atom has been substituted with a fluorine atom.

X″ represents a linear or branched alkylene group in which at least onehydrogen atom has been substituted with a fluorine atom, and thealkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms,and most preferably 3 carbon atoms.

Each of Y″ and Z″ independently represents a linear or branched alkylgroup in which at least one hydrogen atom has been substituted with afluorine atom, and the alkyl group has 1 to 10 carbon atoms, preferably1 to 7 carbon atoms, and most preferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ orthose of the alkyl group for Y″ and Z″ within the above-mentioned rangeof the number of carbon atoms, the more the solubility in a resistsolvent is improved.

Further, in the alkylene group for X″ or the alkyl group for Y″ and Z″,it is preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved. The fluorination ratio of thealkylene group or alkyl group is preferably from 70 to 100%, morepreferably from 90 to 100%, and it is particularly desirable that thealkylene group or alkyl group be a perfluoroalkylene group orperfluoroalkyl group in which all hydrogen atoms are substituted withfluorine atoms.

Furthermore, as an onium salt-based acid generator, a sulfonium salthaving a cation moiety represented by general formula (b-5) or (b-6)shown below may be used.

In formulas (b-5) and (b-6) above, each of R⁴¹ to R⁴⁶ independentlyrepresents an alkyl group, an acetyl group, an alkoxy group, a carboxygroup, a hydroxyl group or a hydroxyalkyl group; each of n₁ to n₅independently represents an integer of 0 to 3; and n₆ represents aninteger of 0 to 2.

With respect to R⁴¹ to R⁴⁶, the alkyl group is preferably an alkyl groupof 1 to 5 carbon atoms, more preferably a linear or branched alkylgroup, and most preferably a methyl group, ethyl group, propyl group,isopropyl group, n-butyl group or tert butyl group.

The alkoxy group is preferably an alkoxy group of 1 to 5 carbon atoms,more preferably a linear or branched alkoxy group, and most preferably amethoxy group or ethoxy group.

The hydroxyalkyl group is preferably the aforementioned alkyl group inwhich one or more hydrogen atoms have been substituted with hydroxygroups, and examples thereof include a hydroxymethyl group, ahydroxyethyl group and a hydroxypropyl group.

If there are two or more of an individual R⁴¹ to R⁴⁶ group, as indicatedby the corresponding value of n₁ to n₆, then the two or more of theindividual R⁴¹ to R⁴⁶ group may be the same or different from eachother.

n₁ is preferably 0 to 2, more preferably 0 or 1, and still morepreferably 0.

It is preferable that n₂ and n₃ each independently represent 0 or 1, andmore preferably 0.

n₄ is preferably 0 to 2, and more preferably 0 or 1.

n₅ is preferably 0 or 1, and more preferably 0.

n₆ is preferably 0 or 1, and more preferably 1.

The anion moiety of the sulfonium salt having a cation moietyrepresented by general formula (b-5) or (b-6) is not particularlylimited, and the same anion moieties for onium salt-based acidgenerators which have been proposed may be used. Examples of such anionmoieties include fluorinated alkylsulfonic acid ions such as anionmoieties (R⁴″SO₃ ⁻) for onium salt-based acid generators represented bygeneral formula (b-1) or (b-2) shown above; and anion moietiesrepresented by general formula (b-3) or (b-4) shown above.

In the present description, an oximesulfonate-based acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation. Suchoximesulfonate acid generators are widely used for a chemicallyamplified resist composition, and can be appropriately selected.

In the formula, each of R³¹ and R³² independently represents an organicgroup.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The alkyl group or the aryl group “hasa substituent” means that part or all of the hydrogen atoms of the alkylgroup or the aryl group is substituted with a substituent.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, stillmore preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbonatoms. As the alkyl group, a partially or completely halogenated alkylgroup (hereinafter, sometimes referred to as a “halogenated alkylgroup”) is particularly desirable. The “partially halogenated alkylgroup” refers to an alkyl group in which part of the hydrogen atoms aresubstituted with halogen atoms and the “completely halogenated alkylgroup” refers to an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of halogen atoms includefluorine atoms, chlorine atoms, bromine atoms and iodine atoms, andfluorine atoms are particularly desirable. In other words, thehalogenated alkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituentor a fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,aryl group, or cyano group is preferable. Examples of the alkyl groupand the aryl group for R³² include the same alkyl groups and aryl groupsas those described above for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

In the formula, R³³ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent or a halogenatedalkyl group.

In the formula, R³⁶ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent or a halogenated alkyl group; and p″ represents 2or 3.

In general formula (B-2), the alkyl group having no substituent or thehalogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbonatoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms thereof fluorinated, more preferably 70% or more, andmost preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthryl group, and a phenanthryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms.Further, the halogenated alkyl group is preferably a fluorinated alkylgroup.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms fluorinated, more preferably 70% or more, still morepreferably 90% or more. A completely fluorinated alkyl group in which100% of the hydrogen atoms are substituted with fluorine atoms isparticularly desirable.

In general formula (B-3), as the alkyl group having no substituent andthe halogenated alkyl group for R³⁶, the same alkyl group having nosubstituent and the halogenated alkyl group described above for R³³ canbe used.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate acid generators include

-   α-(p-toluenesulfonyloxyimino)-benzyl cyanide,-   α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,-   α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,-   α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,-   α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,-   α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,-   α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,-   α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,-   α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide,-   α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,-   α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,-   α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyll acetonitrile,-   α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl acetonitrile,-   α-(tosyloxyimino)-4-thienyl cyanide,    α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,    α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,-   α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,-   α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,-   α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,-   α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,-   α-(ethylsulfonyloxyimino)-ethyl acetonitrile,    α-(propylsulfonyloxyimino)-propyl acetonitrile,    α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,-   α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,-   α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,-   α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,-   α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,-   α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,-   α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,-   α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,-   α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,-   α-(methylsulfonyloxyimino)-phenyl acetonitrile,-   α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,-   α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,-   α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,-   α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,-   α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, and-   α-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate-based acid generators disclosed in WO 2004/074242A2(Examples 1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following can be used.

Of the aforementioned diazomethane acid generators, specific examples ofsuitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane acid generators disclosed in Japanese UnexaminedPatent Application, First Publication No. Hei 11-035551, JapaneseUnexamined Patent Application, First Publication No. Hei 11-035552 andJapanese Unexamined Patent Application, First Publication No. Hei11-035573 may be preferably used.

Furthermore, as examples of poly(bis-sulfonyl)diazomethanes, thosedisclosed in Japanese Unexamined Patent Application, First PublicationNo. Hei 11-322707, including1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may be given.

As the component (B), one type of acid generator may be used, or two ormore types of acid generators may be used in combination.

In the present invention, as the component (B), it is preferable to usean onium salt having a fluorinated alkylsulfonic acid ion as the anionmoiety.

In the positive resist composition of the present invention, the amountof the component (B) relative to 100 parts by weight of the component(A) is preferably 0.5 to 50 parts by weight, and more preferably 1 to 40parts by weight. By ensuring that the amount of the component (B) iswithin the above-mentioned range, formation of a resist pattern can besatisfactorily performed. Further, by virtue of the above-mentionedrange, a uniform solution can be obtained and the storage stabilitybecomes satisfactory.

<Optional Components>

The positive resist composition of the present invention may furthercontain a nitrogen-containing organic compound (D) (hereafter referredto as the component (D)) as an optional component.

As the component (D), there is no particular limitation as long as itfunctions as an acid diffusion control agent, i.e., a quencher whichtraps the acid generated from the component (B) upon exposure. Amultitude of these components (D) have already been proposed, and any ofthese known compounds may be used As the component (D), an amine such asan aliphatic amine, an aromatic amine or the like is preferable, analiphatic amine is more preferable, and a secondary aliphatic amine or atertiary aliphatic amine is particularly desirable. The term “aliphaticcyclic group” refers to a monocyclic group or polycyclic group that hasno aromaticity. An aliphatic amine is an amine having one or morealiphatic groups, and the aliphatic groups preferably have 1 to 20carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 20 carbon atoms (i.e., alkylaminesor alkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decanylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine,tri-n-octanolamine, stearyldiethanolamine and laurildiethanolamine.Among these, trialkylamines and/or alkylalcoholamines are preferable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine andtris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine.

Examples of aromatic amines include aniline, 1,8-naphthalenediamine,pyridine, 4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazoleand derivatives thereof, as well as diphenylamine, triphenylamine andtribenzylamine.

These compounds can be used either alone, or in combinations of two ormore different compounds.

The component (D) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A). By ensuring that the amount of the component (D) iswithin the above-mentioned range, the shape of the resist pattern andthe post exposure stability of the latent image formed by thepattern-wise exposure of the resist layer are improved.

Furthermore, in the positive resist composition of the presentinvention, for preventing any deterioration in sensitivity, andimproving the resist pattern shape and the post exposure stability ofthe latent image formed by the pattern-wise exposure of the resistlayer, at least one compound (E) (hereafter referred to as the component(E)) selected from the group consisting of an organic carboxylic acid,or a phosphorus oxo acid or derivative thereof can be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids or derivatives thereof includephosphoric acid, phosphonic acid and phosphinic acid. Among these,phosphonic acid is particularly desirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esterssuch as phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

[Component (F)]

The positive resist composition of the present invention may include afluorine-containing polymeric compound (F) (hereafter, referred to as“component (F)”). By including the component (F), thehydrophilicity/hydrophobicity of the resist film surface can be adjustedwithout impairing the lithography properties.

For example, by blending the component (F), the hydrophobicity of theresist film surface can be enhanced during exposure, thereby renderingthe composition suitable for immersion exposure.

Further, by blending a component (F) having a base dissociable group(described later), since the component (F) exhibits enhancedhydrophilicity by the action of an alkali developing solution, thehydrophilicity of the surface of the resist film formed is enhancedduring development.

Furthermore, by blending a component (F) having an acid dissociablegroup (described later), since the component (F) exhibits enhancedhydrophilicity by the action of acid generated from the component (B),the hydrophilicity of the exposed surface of the resist film formed isenhanced when conducting exposure and PEB.

When the component (F) is blended, it is preferable that the component(A) has no fluorine atom.

In the present invention, the component (F) preferably includes astructural unit (f1) represented by general formula (f1-1) shown below.

In formula (f1-1), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Q⁰represents a single bond or a divalent linking group; R⁷⁰ represents anorganic group having a fluorine atom; and the plurality of R may be thesame or different from each other.

(Structural Unit (f1))

In general formula (f1-1), R is the same as defined for R in generalformula (a0-1), and a hydrogen atom or a methyl group is preferable.

In formula (f1-1), Q⁰ represents a single bond or a divalent linkinggroup.

As examples of the divalent linking group for Q⁰, the same groups asthose described above for R² in formula (a0-1) can be given. Preferableexamples include a divalent hydrocarbon group which may have asubstituent and a divalent linking group containing a hetero atom.

As the divalent hydrocarbon group which may have a substituent, alinear, branched or cyclic divalent aliphatic hydrocarbon group or adivalent aromatic hydrocarbon group is preferable, and a methylenegroup, and ethylene group, —CH(CH₃)—, a group in which one hydrogen atomhas been removed from a tetracyclododecyl group, or an aromatichydrocarbon group in which one hydrogen atom has been removed from aphenyl group is particularly desirable.

Among the aforementioned examples, as Q⁰, a single bond or a divalentlinking group containing a hetero atom is preferable, and a single bondor a combination of a divalent non-hydrocarbon group containing a heteroatom with a divalent aliphatic hydrocarbon group is particularlydesirable.

In general formula (f1-1), R⁷⁰ represents an organic group which mayhave a fluorine atom. However, when R⁷⁰ has no fluorine atom, Q⁰ has afluorine atom.

An “organic group having a fluorine atom” refers to an organic group inwhich part or all of the hydrogen atoms have been substituted with afluorine atom.

As an example of an organic group represented by R⁷⁰ which may have afluorine atom, a hydrocarbon group which may have a fluorine atom can begiven.

The hydrocarbon group which may have a fluorine atom may be linear,branched or cyclic.

R⁷⁰ preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbonatoms, and most preferably 1 to 10 carbon atoms.

It is preferable that the organic group having a fluorine atomrepresented by R⁷⁰ has 25% or more of the hydrogen atoms within theorganic group fluorinated, more preferably 50% or more, and mostpreferably 60% or more, as the hydrophobicity of the resist film duringimmersion exposure is enhanced.

Preferable examples of R⁷⁰ include a base dissociable group, an aciddissociable group, and a group other than base dissociable groups andacid dissociable groups.

A base dissociable group refers to a group that is decomposable (—O—R⁷°is dissociated) by the action of an alkali developing solution. Theexpression “decomposable in an alkali developing solution” means thatthe group is decomposable by the action of an alkali developing solution(preferably decomposable by action of a 2.38% by weight aqueous solutionof tetramethylammonium hydroxide (TMAH) at 23° C.), and exhibitsincreased alkali solubility in the alkali developing solution. Thereason for this is that the ester bond [—C(═O)—O—R⁷⁰] is decomposed(hydrolyzed) by the action of a base (alkali developing solution),thereby forming a hydrophilic group [—C(═O)—OH] (—O—R⁷⁰ is dissociated).

Preferable examples of the base dissociable group include fluorinatedhydrocarbon groups which may or may not have a substituent. Amongfluorinated hydrocarbon groups, a fluorinated, saturated hydrocarbongroup or a fluorinated, unsaturated hydrocarbon group is preferable, anda fluorinated, saturated hydrocarbon group is particularly desirable.

R⁷⁰ may be linear, branched or cyclic, and is preferably linear orbranched.

R⁷⁰ preferably has 1 to 20 carbon atoms, more preferably 1 to 15, stillmore preferably 1 to 10, and most preferably 1 to 5.

It is preferable that the organic group having a fluorine atomrepresented by R⁷⁰ has 25% or more of the hydrogen atoms within theorganic group fluorinated, more preferably 50% or more, and mostpreferably 60% or more, as the hydrophobicity of the resist film duringimmersion exposure is enhanced.

An acid dissociable group is a group that is dissociated by an acid toincrease solubility in an alkali developing solution. The aciddissociable group will be described later in detail. When the aciddissociable group contains no fluorine atom, Q⁰ has a fluorine atom.

Examples of the group other than acid dissociable groups and basedissociable groups include linear, branched or cyclic alkyl groups of 3to 15 carbon atoms (excluding groups containing a tertiary carbon atom).In such a case, Q⁰ has a fluorine atom.

Acid Dissociable Group

The acid dissociable group for R⁷⁰ is not particularly limited as longas it is an organic group that is dissociable by the action of an acid,and examples thereof include a cyclic or chain-like tertiary alkylester-type acid dissociable group; and an acetal-type acid dissociablegroup, such as an alkoxyalkyl group. Among these, R⁷⁰ is preferably atertiary alkyl ester-type acid dissociable group, and more preferably astructural unit represented by general formula (IV-1) shown below.

In formula (IV-1), at least one of R²⁰¹ represents a linear or branchedalkyl group of 1 to 4 carbon atoms, and the or each remaining R²⁰¹independently represents a linear or branched alkyl group of 1 to 4carbon atoms or a monovalent aliphatic cyclic group of 4 to 20 carbonatoms, or the or each remaining R²⁰¹ may be mutually bonded to form adivalent aliphatic cyclic group of 4 to 20 carbon atoms together withthe carbon atoms bonding each other; and the plurality of R²⁰¹ may bethe same or different from each other.

As the aliphatic cyclic group for R²⁰¹ in general formula (IV-1), forexample, a group in which one or more hydrogen atoms have been removedfrom a monocycloalkane or a polycycloalkane such as a bicycloalkane, atricycloalkane or a tetracycloalkane can be used. Examples of suchgroups include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane or cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Specific examples of such groupsinclude a cyclopentyl group, a cyclohexyl group, a norbornyl group andan adamantyl group.

Examples of linear or branched alkyl groups of 1 to 4 carbon atomsinclude a methyl group, an ethyl group, a propyl group, an isopropylgroup, an n-butyl group, an isobutyl group and a tert-butyl group.

Examples of the acid dissociable group represented by general formula(IV-1) in which a plurality of R²⁰¹ each independently represents alinear or branched alkyl group of 1 to 4 carbon atoms include atert-butyl group, a tert-pentyl group and a tert-hexyl group.

Examples of the acid dissociable group represented by general formula(IV-1) in which at least one of R²⁰¹ represents a linear or branchedalkyl group of 1 to 4 carbon atoms, and the or each remaining R²⁰¹independently represents a linear or branched alkyl group of 1 to 4carbon atoms or a monovalent aliphatic cyclic group of 4 to 20 carbonatoms include a 1-(1-adamantyl)-1-methylethyl group, a1-(1-adamantyl)-1-methylpropyl group, a 1-(1-adamantyl)-1-methylbutylgroup, a 1-(1-adamantyl)-1-methylpentyl group, a1-(1-cyclopentyl)-1-methylethyl group, a1-(1-cyclopentyl)-1-methylpropyl group, a1-(1-cyclopentyl)-1-methylbutyl group, a1-(1-cyclopentyl)-1-methylpentyl group, a 1-(1-cyclohexyl)-1-methylethylgroup, a 1-(1-cyclohexyl)-1-methylpropyl group, a1-(1-cyclohexyl)-1-methylbutyl group, and a1-(1-cyclohexyl)-1-methylpentyl group.

Examples of the acid dissociable group represented by general formula(IV-1) in which one R²⁰¹ group among the plurality of R²⁰¹ groupsrepresents a linear or branched alkyl group of 1 to 4 carbon atoms, andthe remaining two R²⁰¹ groups are mutually bonded to form a divalentaliphatic cyclic group of 4 to 20 carbon atoms together with the carbonatoms bonding each other include a 2-alkyl-2-adamantyl group such as a2-methyl-2-adamantyl group or a 2-ethyl-2-adamantyl group, and a1-alkyl-1-cycloalkyl group such as a 1-methyl-1-cyclopentyl group, a1-ethyl-1-cyclopentyl group, a 1-methyl-1-cyclohexyl group, or a1-ethyl-1-cyclohexyl group.

Among these examples, as the acid dissociable group represented bygeneral formula (IV-1), a group in which one R²⁰¹ group among theplurality of R²⁰¹ groups represents a linear or branched alkyl group of1 to 4 carbon atoms, and two of the R²⁰¹ groups are mutually bonded toform a divalent aliphatic cyclic group of 4 to 20 carbon atoms togetherwith the carbon atoms bonding each other is preferable, and a2-methyl-2-adamantyl group is particularly desirable.

Each R²⁰¹ group may have a substituent as long as the group representedby general formula (IV-1) functions as an acid dissociable group. As anexample of the substituent, a halogen atom such as a fluorine atom canbe given.

Specific examples of preferable units for the structural unit (f1) areshown below.

Hereinbelow, a structural unit in which R⁷⁰ in general formula (f1-1)represents a “base dissociable group” is referred to as a structuralunit (f11), and a structural unit in which R⁷⁰ represents an aciddissociable group is referred to as a structural unit (f12).

(Structural Unit (f11))

Specific examples of preferable structural units for the structural unit(f11) include structural units represented by general formula (f11-1) or(f11-2) shown below.

In the formulas above, each R independently represents a hydrogen atom,an alkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1to 5 carbon atoms; Z represents a divalent organic group; A_(aryl)represents an aromatic cyclic group which may have a substituent; X₀₁represents a single bond or a divalent linking group; and each R⁷¹independently represents a base dissociable group. However, when R⁷¹ hasno fluorine atom, Z has a fluorine atom in formula (f11-1), and A_(aryl)or X₀₁ has a fluorine atom in formula (f11-2).

In general formula (f11-1) or (f11-2), R is the same as defined above,and is preferably a hydrogen atom or a methyl group.

The base dissociable group for R⁷¹ is the same as defined in theexplanation above, more preferably an alkyl group of 1 or 2 carbon atomsor a fluorinated hydrocarbon group of 1 to 5 carbon atoms, and a methylgroup, —CH₂—CF₃, —CH₂—CF₂—CF₃, —CH(CF₃)₂, or —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃ isparticularly desirable. When R⁷¹ represents a methyl group, an ethylgroup or a fluorinated hydrocarbon group, the —O—R⁷¹ group is a basedissociable group which is dissociable by the action of an alkalideveloping solution.

In general formula (f11-1), Z represents a divalent organic group.

Preferable examples of Z include the aforementioned hydrocarbon groupwhich may have a substituent, and a group containing a hetero atom.

In general formula (f11-2), A_(aryl) represents an aromatic cyclic groupwhich may have a substituent. A specific example of A_(aryl) includes anaromatic hydrocarbon ring (which may have a substituent) having twohydrogen atoms removed therefrom.

The ring skeleton of the aromatic cyclic group for A_(aryl) preferablyhas 6 to 15 carbon atoms. Examples of the ring skeleton include abenzene ring, a naphthalene ring, a phenanthrene ring and an anthracenering. Among these, a benzene ring or a naphthalene ring is particularlydesirable.

Examples of substituents which an aromatic cyclic group for A_(aryl) mayhave include a halogen atom, an alkyl group, an alkoxy group, ahalogenated alkyl group of 1 to 5 carbon atoms, and an oxygen atom (═O).Examples of halogen atoms include a fluorine atom, a chlorine atom, aniodine atom and a bromine atom. As the substituent which an aromaticcyclic group for A_(aryl) may have, a fluorine atom is preferable.

A_(aryl) may be either an aromatic cyclic group having no substituent,or an aromatic cyclic group having a substituent, although an aromaticcyclic group having no substituent is preferable.

When A_(aryl) is an aromatic cyclic group having a substituent, thenumber of the substituent may be either 1 or at least 2, preferably 1 or2, and more preferably 1.

In formula (f11-2), X₀₁ represents a single bond or a divalent linkinggroup. Examples of divalent linking groups include an alkylene group of1 to 10 carbon atoms, —O—, —C(═O)—, —C(═O)—O—, a carbonate bond(—O—C(═O)—O—), —NH—C(═O)—, and a combination of these groups, and acombination of —O— with an alkylene group of 1 to 10 carbon atoms isparticularly desirable.

Examples of alkylene groups of 1 to 12 carbon atoms include linear,branched or cyclic alkylene groups, and a linear or branched alkylenegroup of 1 to 5 carbon atoms and a cyclic alkylene group of 4 to 12carbon atoms are preferable.

X₀₁ is preferably a single bond, —(R⁷⁷)_(A0)—O—[C(═O)]_(b0)—R⁷⁸—, or—C(═O)—O—R⁷⁹—.

Each of R⁷⁷, R⁷⁸ and R⁷⁰ independently represents a linear, branched orcyclic alkylene group of 1 to 10 carbon atoms, and preferably a linearor branched alkylene group of 1 to 5 carbon atoms or a cyclic alkylenegroup of 4 to 10 carbon atoms.

a0 represents 0 or an integer of 1 to 5.

b0 represents 0 or 1.

Preferable examples of the structural unit (f11) include structuralunits represented by general formulas (f11-1-1) to (f11-1-5) or(f11-2-1) to (f11-2-4) shown below.

In general formulas (f11-1-1) to (f11-1-5) and (f11-2-1) to (f11-2-4), Rand R⁷¹ are the same as defined above; each of R⁸¹ and R⁸² independentlyrepresents a hydrogen atom, a fluorine atom, an alkyl group of 1 to 5carbon atoms or a fluorinated alkyl group of 1 to 5 carbon atoms; whena1 is 2 or more, the plurality of R⁸¹ and R⁸² may be the same ordifferent from each other; each of a1 to a3, a5, a7, a9 and a11 to a13independently represents an integer of 1 to 5 carbon atoms; each of a4,a6, a8 and a10 independently represents 0 or an integer of 1 to 5: b1 tob5 independently represents 0 or 1; R⁸⁰ represents a substituent; erepresents an integer of 0 to 2; and A₁ represents a cyclic alkylenegroup of 4 to 20 carbon atoms.

In general formula (f11-1-1), a1 is preferably 1 to 3, more preferably 1or 2.

In general formula (f11-1-2), it is preferable that each of a2 and a3independently represent 1 to 3, more preferably 1 or 2. b1 represents 0or 1.

In general formula (f11-1-3), a4 is preferably 0 or 1 to 3, morepreferably 0, 1 or 2, and most preferably 0 or 1. a5 is preferably 1 to3, more preferably 1 or 2. As the substituent for R⁸⁰, for example, ahalogen atom, a lower alkyl group, an alkoxy group of 1 to 5 carbonatoms, a halogenated lower alkyl group, or an oxygen atom (═O) can beused. Examples of halogen atoms include a fluorine atom, a chlorineatom, an iodine atom and a bromine atom. e is preferably 0 or 1, andmost preferably 0 from an industrial viewpoint. b2 is preferably 0.

In general formula (f11-1-4), a6 is preferably 0 or 1 to 3, morepreferably 0, 1 or 2, and most preferably 0 or 1. a7 is preferably 1 to3, more preferably 1 or 2. b3 is preferably 0. R⁸⁰ and e are the same asdefined above.

In general formula (f11-1-5), A₁ represents a cyclic alkylene group of 4to 20 carbon atoms, preferably a cyclic alkylene group of 5 to 15 carbonatoms, and more preferably a cyclic alkylene group of 6 to 12 carbonatoms. Specific examples include the aforementioned “cyclic aliphatichydrocarbon groups” described above in relation to the aforementionedhydrocarbon group which may have a substituent.

In general formula (f11-2-1), a8 is preferably 0 or 1 to 3, morepreferably 0, 1 or 2, and most preferably 0 or 1. a9 is preferably 1 to3, more preferably 1 or 2. b4 is preferably 0. R⁸⁰ and e are the same asdefined above.

In general formula (f11-2-2), a10 is preferably 0 or 1 to 3, morepreferably 0, 1 or 2, and most preferably 0 or 1. a11 is preferably 1 to3, more preferably 1 or 2. b5 is preferably 0. R⁸⁰ and e are the same asdefined above.

In general formula (f11-2-3), a12 is preferably 1 to 3, more preferably1 or 2. R⁸⁰ and e are the same as defined above.

In general formula (f11-2-4), a13 is preferably 1 to 3, more preferably1 or 2. R⁸⁰ and e are the same as defined above.

Specific examples of structural units represented by the above generalformulas (f11-1-1) to (f11-1-5) and (f11-2-1) to (f11-2-4) are shownbelow.

As the structural unit (f11), at least one structural unit selected fromthe group consisting of structural units represented by general formulas(f11-1-1) to (f11-1-5) and (f11-2-1) to (f11-2-4) is preferable, morepreferably at least one structural unit selected from the groupconsisting of structural units represented by general formulas (f11-1-1)to (f-1-1-5), (f11-2-1) and (f11-2-2), and most preferably at least onestructural unit selected from the group consisting of structural unitsrepresented by general formulas (f11-1-1), (f11-1-5) and (f11-2-2).

As the structural unit (f11), one type of structural unit may be usedalone, or two or more structural units may be used in combination.

In the component (F), the amount of the structural unit (f11) based onthe combined total of all structural units constituting the component(F) is preferably 10 to 90 mol %, more preferably 20 to 90 mol %, stillmore preferably 30 to 90 mol %, and may be even 100 mol %. When theamount of the structural unit (f11) is at least as large as the lowerlimit of the above-mentioned range, in the formation of a resistpattern, the hydrophobicity during immersion exposure is enhanced.

(Structural Unit (f12))

Specific examples of preferable structural units for the structural unit(f12) include structural units represented by general formula (f12-1)shown below.

In formula (f12-1), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms;Q^(0,) represents a single bond or a divalent linking group; and R⁷²represents an acid dissociable group.

In general formula (f12-1), R is the same as defined above, and ispreferably a hydrogen atom or a methyl group.

Examples of the acid dissociable group for R⁷² include the same groupsas those described above in the explanation of the acid dissociablegroup for R⁷⁰.

Preferable examples of a structural unit represented by general formula(f12-1) in which Q^(0,) is a single bond include structural unitsrepresented by general formulas (f12-1-1) to (f12-1-4) shown below.

In general formula (f12-1), when Q^(0,) represents a divalent linkinggroup, examples of the divalent linking group include the same groups asthose described above for X₀₁ in general formula (f11-2), and a divalentaromatic hydrocarbon group. Examples of divalent aromatic hydrocarbongroups include aromatic hydrocarbon groups of 6 to 20 carbon atoms suchas groups in which two hydrogen atoms have been removed from a benzenering, a naphthalene ring or an anthracene ring.

In a structural unit (f12), Q^(0,) is preferably a single bond or—C(═O)—O—R^(d)— (in the formula, R^(d) represents a linear or branchedalkylene group of 1 to 10 carbon atoms which may contain an oxygen atom,and the alkylene group may be fluorinated), and more preferably a singlebond.

Preferable examples of a structural unit represented by general formula(f12-1) in which Q^(0,) is —C(═O)—O—R^(d)— include structural unitsrepresented by general formulas (f12-1-5) to (f12-1-11) shown below.

In the formulas shown below, R is the same as defined above, and ispreferably a hydrogen atom or a methyl group.

As the structural unit (f12), at least one structural unit selected fromthe group consisting of structural units represented by general formulas(f12-1-1) to (f12-1-11) are preferable, and at least one structural unitselected from the group consisting of structural units represented bygeneral formulas (f12-1-1) to (f12-1-4) is particularly desirable.

In the component (F), as the structural unit (f12), one type ofstructural unit may be used alone, or two or more types of structuralunits may be used in combination.

When the component (F) includes the structural unit (f12), the amount ofthe structural unit (f12) based on the combined total of all structuralunits constituting the component (F) is preferably 10 to 100 mol %, morepreferably 30 to 90 mol %, and most preferably 50 to 90 mol %. When theamount of the structural unit (f12) is at least as large as the lowerlimit of the above-mentioned range, in the formation of a resistpattern, the hydrophobicity during exposure is enhanced. Further, thelithographic properties are also improved. On the other hand, by whenthe amount is no more than the upper limit of the above-mentioned range,a good balance can be achieved with the other structural units. Thestructural unit (f12) can be used as a homopolymer.

[Other Structural Unit]

The component (F) may contain a structural unit other than theaforementioned structural unit (f1) (hereafter, referred to as“structural unit (f2)”), as long as the effects of the present inventionare not impaired.

Preferable examples of the structural unit (f2) include the samestructural units as those described above for the structural unit (a1).A structural unit represented by the aforementioned formula (a1-0-11) ismore preferable.

In formula (a1-0-11) for the structural unit (f2), the alkyl grouprepresented by R²¹

is preferably an ethyl group, an n-propyl group or an n-butyl group.

The aliphatic monocyclic group formed by R²² and the carbon atom bondedthereto is preferably a 8- to 11-membered ring, and more preferably a 8-to 10-membered ring.

In the component (F), as the structural unit (f2), one type ofstructural unit may be used alone, or two or more types of structuralunits may be used in combination.

When the component (F) includes the structural unit (f2), the amount ofthe structural unit (f2) based on the combined total of all structuralunits constituting the component (F) is preferably 5 to 80 mol %, morepreferably 10 to 60 mol %, still more preferably 15 to 50 mol %, andmost preferably 20 to 40 mol %. When the amount of the structural unit(f2) is at least as large as the lower limit of the above-mentionedrange, the characteristic feature of exhibiting hydrophobicity duringimmersion exposure, but then exhibiting increased hydrophilicity duringexposure and post exposure baking (PEB) is improved. Moreover, formationof bridge-type defects in a line and space pattern or formation of “NotOpen” defects in which a portion of, or all of, a contact hole patternis not open can be suppressed. Furthermore, the proportion ofhydrocarbon groups within the component (F) increases and the watertracking ability during immersion exposure using a scanning-typeimmersion exposure apparatus is improved. On the other hand, when theamount is no more than the upper limit of the above-mentioned range, agood balance can be achieved with the structural unit (f1).

The component (F) may include a structural unit other than thestructural unit (f1) and the structural unit (f2) (hereafter, frequentlyreferred to as “structural unit (f3)”), as long as the effects of thepresent invention are not impaired.

There are no particular limitations on the structural unit (f3),provided the structural unit is derived from a compound that iscopolymerizable with the compound that derives the structural unit (f1)and the compound that derives the structural unit (f2). Examples of suchstructural units include structural units which have been proposed forthe base resin of a conventional chemically amplified resist (such asthe aforementioned structural units (a2) to (a4) which do not fall underthe category of the structural units (f1) and (f2)).

In the component (F), as the structural unit (f3), one type ofstructural unit may be used alone, or two or more types of structuralunits may be used in combination.

When the component (F) includes the structural unit (f3), the amount ofthe structural unit (f3) based on the combined total of all structuralunits constituting the component (F) is preferably 1 to 25 mol %, morepreferably 5 to 20 mol %, and most preferably 10 to 20 mol %.

In the present invention, the component (F) is preferably a polymerincluding the structural unit (f11), a polymer including the structuralunit (f12), or a polymer including the structural unit (f1).

Examples of such polymers include a polymer consisting of one structuralunit (f11), a copolymer consisting of at least two structural units(f11), a polymer consisting of one structural unit (f12), and acopolymer consisting of a structural unit (f11) and a structural unit(f2).

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (F)is not particularly limited, but is preferably 2,000 to 50,000, morepreferably 3,000 to 30,000, and most preferably 4,000 to 25,000. Whenthe weight average molecular weight is no more than the upper limit ofthe above-mentioned range, the resist composition exhibits asatisfactory solubility in a resist solvent. On the other hand, when theweight average molecular weight is at least as large as the lower limitof the above-mentioned range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, morepreferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is thenumber average molecular weight.

As the component (F), one type of resin may be used, or two or moretypes of resins may be used in combination.

In the positive resist composition of the present invention, the amountof the component (F) relative to 100 parts by weight of the component(A) is preferably 0.1 to 50 parts by weight, more preferably 0.1 to 40parts by weight, still more preferably 0.5 to 30 parts by weight, andmost preferably 0.5 to 15 parts by weight.

When the amount of the component (F) is at least as large as the lowerlimit of the above-mentioned range, the effects of blending thecomponent (F) can be satisfactorily achieved. On the other hand, byensuring that the amount of the component (F) is no more than the upperlimit of the above-mentioned range, the lithography properties areimproved.

If desired, other miscible additives can also be added to the positiveresist composition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, surfactants for improving the applicability, dissolutioninhibitors, plasticizers, stabilizers, colorants, halation preventionagents, and dyes.

The positive resist composition of the present invention can be preparedby dissolving the materials for the resist composition in an organicsolvent (hereafter, frequently referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone;

ketones such as acetone, methyl ethyl ketone, cyclohexanone,methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone;

polyhydric alcohols, such as ethylene glycol, diethylene glycol,propylene glycol and dipropylene glycol;

compounds having an ester bond, such as ethylene glycol monoacetate,diethylene glycol monoacetate, propylene glycol monoacetate, anddipropylene glycol monoacetate; polyhydric alcohol derivatives includingcompounds having an ether bond, such as a monoalkylether (e.g.,monomethylether, monoethylether, monopropylether or monobutylether) ormonophenylether of any of these polyhydric alcohols or compounds havingan ester bond (among these, propylene glycol monomethyl ether acetate(PGMEA) and propylene glycol monomethyl ether (PGME) are preferable);

cyclic ethers such as dioxane; esters such as methyl lactate, ethyllactate (EL), methyl acetate, ethyl acetate, butyl acetate, methylpyruvate, ethyl pyruvate, methyl methoxypropionate, and ethylethoxypropionate;

and aromatic organic solvents such as anisole, ethylbenzylether,cresylmethylether, diphenylether, dibenzylether, phenetole,butylphenylether, ethylbenzene, diethylbenzene, pentylbenzene,isopropylbenzene, toluene, xylene, cymene and mesitylene.

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, propylene glycol monomethyl ether acetate (PGMEA),propylene glycol monomethyl ether (PGME) and ethyl lactate (EL) arepreferable.

Further, among the mixed solvents, a mixed solvent obtained by mixing

PGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL is mixed as the polar solvent, the PGMEA:EL weightratio is preferably from 1:9 to 9:1, and more preferably from 2:8 to8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME is preferably from 1:9 to 9:1, more preferably from 2:8 to8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the organic solvent is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate, depending on the thickness of thecoating film. In general, the organic solvent is used in an amount suchthat the solid content of the resist composition becomes within therange from 1 to 20% by weight, and preferably from 2 to 15% by weight.

The positive resist composition of the present invention described aboveand the component (A1) or (A1′) blended in the positive resistcomposition are novel, and are essentially unknown in the art.

By the positive resist composition of the present invention, a resistfilm can be formed on a support such as a substrate with excellentadhesion.

Further, by the positive resist composition of the present invention,the formed pattern exhibits excellent properties with respect to thepattern shape (e.g., circularity of the holes of a hole pattern),in-plane uniformity (CDU), line width roughness (LWR), rectangularity ofthe cross-section, and the like. LWR refers to the phenomenon in whichthe line widths of a line pattern formed using a resist compositionbecomes heterogeneous, and improvement in this characteristic becomesmore important as the pattern becomes finer.

Further, by the positive resist composition of the present invention, aresist pattern can be formed with excellent mask reproducibility (e.g.,excellent mask error factor (MEF)). The MEF is a parameter thatindicates how faithfully mask patterns of differing dimensions can bereproduced by using the same exposure dose with fixed pitch and changingthe mask size (i.e., mask reproducibility).

Further, in the formation of a resist pattern using the positive resistcomposition of the present invention, the problems of scums generated asresidue of the exposed portions of the resist film which cannot besatisfactorily dissolved in an alkali developing solution can be solved.

In the present invention, the reasons why the above-mentioned effectscan be achieved have not been elucidated yet. However, one of thereasons is presumed that by virtue of the structural unit (a0) having aspecific lactone-containing cyclic group bonded to the terminal of arelatively long side chain, the component (B) can be uniformlydistributed in the resist film, thereby resulting in the improvement inlithography properties.

Further, in the positive resist composition of the present invention,the hydrophilicity of the resist film surface is increased upon cominginto contact with an alkali developing solution. Therefore, when aresist film formed using the positive resist composition is subjected toexposure and alkali developing, the hydrophilicity of the unexposedportions is increased.

In conventional techniques, when the resist film exhibits highhydrophobicity, defects (water mark defects caused by the influence ofthe immersion medium such as water, bridge defects, not-open defects,adhesion-type defects) are likely to be generated on the resist filmsurface following developing. In contrast, in the resist film formedusing the positive resist composition of the present invention, sincethe hydrophilicity of the resist film surface of unexposed portions isincreased during alkali developing, generation of defects can bereduced. In the present invention, effect of reducing generation ofadhesion-type defects is particularly expected.

<<Method of Forming a Resist Pattern>>

The method of forming a resist pattern according to the presentinvention includes: applying a positive resist composition of thepresent invention to a substrate to form a resist film on the substrate;conducting exposure of the resist film; and developing the resist filmto form a resist pattern.

More specifically, the method for forming a resist pattern according tothe present invention can be performed, for example, as follows.

More specifically, the method for forming a resist pattern according tothe present invention can be performed, for example, as follows.Firstly, a positive resist composition of the present invention isapplied onto a substrate using a spinner or the like, and a prebake(post applied bake (PAB)) is conducted under temperature conditions of80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds to forma resist film. Then, for example, using an ArF exposure apparatus or thelike, the resist film is selectively exposed with an ArF exposureapparatus, an electron beam exposure apparatus, an EUV exposureapparatus or the like through a mask pattern or directly irradiated withelectron beam without a mask pattern, followed by post exposure bake(PEB) under temperature conditions of 80 to 150° C. for 40 to 120seconds, preferably 60 to 90 seconds. Subsequently, developing isconducted using an alkali developing solution such as a 0.1 to 10% byweight aqueous solution of tetramethylammonium hydroxide (TMAH),preferably followed by rinsing with pure water, and drying. If desired,bake treatment (post bake) can be conducted following the developing. Inthis manner, a resist pattern that is faithful to the mask pattern canbe obtained.

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) can be used.

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as ArF excimer laser,KrF excimer laser,

F₂ excimer laser, extreme ultraviolet rays (EUV), vacuum ultravioletrays (VUV), electron beam (EB), X-rays, and soft X-rays. The positiveresist composition of the present invention is effective to KrF excimerlaser, ArF excimer laser, EB and EUV, and particularly effective to ArFexcimer laser.

The exposure of the resist film can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long at it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

<<Polymeric Compound>>

The polymeric compound of the present invention includes a component(A1′) containing an acid dissociable, dissolution inhibiting groupwithin the structure thereof and including a structural unit (a0)represented by general formula (a0-1) shown below and a structural unit(a2) derived from an acrylate ester containing a lactone-containingcyclic group exclusive of the structural unit (a0); or a component (A1)including a structural unit (a0) represented by general formula (a0-1)shown below and a structural unit (a1) derived from an acrylate estercontaining an acid dissociable, dissolution inhibiting group exclusiveof the structural unit (a0) and the structural unit (a2).

The explanation of the polymeric compound of the present invention isthe same as the explanation of the components (A1) and (A1′) of thepositive resist composition of the present invention described above.

In the formula, R¹ represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R² represents a divalent linking group;each R′ independently represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms, an alkoxy group of 1 to 5 carbon atoms or —COOR″,wherein R″ represents a hydrogen atom or an alkyl group; and A″represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5carbon atoms which may contain an oxygen atom or a sulfur atom.

Examples

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

In the following examples, a unit represented by a chemical formula (1)is designated as “compound (1)”, and the same applies for compoundsrepresented by other formulas.

Monomer Synthesis Example 1 Synthesis of Compound (2)

The compound (2) used in the polymer synthesis examples described laterwas synthesized as follows.

300 ml of a THF solution containing 30.23 g (151.71 mmol) of an alcohol(1), 30.23 g (157.71 mmol) of ethyldiisopropylaminocarbodiimide (EDCI)hydrochloride and 0.6 g (5 mmol) of dimethylaminopyridine was added to a500 ml three-necked flask in nitrogen atmosphere, and 16.67 g (115.66mmol) of a precursor (1) was added thereto while cooling with ice (0°C.), followed by stirring at room temperature for 12 hours.

After conducting thin-layer chromatography to confirm that the rawmaterials had been consumed, 50 ml of water was added to stop thereaction. Then, the reaction solvent was concentrated under reducedpressure, and extraction was conducted with ethyl acetate. The obtainedorganic phase was washed with saturated sodium hydrogencarbonate andwater. Thereafter, the solvent was distilled off under reduced pressure,and the resulting product was dried, thereby obtaining 26.06 g of thecompound (2). The results of instrumental analysis of the obtainedcompound (2) were as follows.

¹H-NMR(CDCl₃,400 MHz):δ(ppm)=6.23(s,1H,Ha or b), 5.67(s,1H,Ha or b),4.40-4.71(m,3H,Hd,He), 1.38-2.74(m,15H,Hc,Hf,Hg,Hh,Hi,Hj,Hk,Hl)

Monomer Synthesis Example 1-2 Synthesis of Compound (2′)

The same procedure as in Monomer Synthesis Example 1 was performed,except that the alcohol (1) was changed to alcohol (1′) shown below,thereby obtaining a compound (2′).

The results of instrumental analysis of the obtained compound (2′) wereas follows.

¹H-NMR(CDCl₃,400 MHz):δ(ppm)=6.13(s,1H,Ha or Hb), 5.58(t,1H,Ha or Hb),4.96(s,1H,He or Hf), 4.60(s,2H,Hd), 4.06(d,1H,He or Hf), 3.72(m,2H,Hl),3.63(s,3H,Hm), 2.47-2.87(m,4H,Hg,Hi,Hj,Hk), 1.90(s,3H,Hc),1.79(d,1H,Hh), 1.49(d,1H,Hh)

Monomer Synthesis Example 2 Synthesis of Compound (11)

The compound (11) used in the polymer synthesis examples described laterwas synthesized as follows.

37.6 g (494 mmol) of glycolic acid, 700 mL of DMF, 86.5 g (626 mmol) ofpotassium carbonate, and 28.3 g (170 mmol) of potassium iodide wereadded to a 2L three-necked flask equipped with a thermometer, a coolingpipe, and a stirrer, followed by stirring at room temperature for 30minutes. Then, 300 ml of a dimethylformamide solution containing 100 g(412 mmol) of 2-methyl-2-adamantyl chloroacetate was gradually addedthereto. The resultant was heated to 40° C., and stirred for 4 hours.Subsequently, 2,000 ml of diethylether was added to the reactionmixture, followed by filtration. The resulting solution was washed with500 ml of distilled water three times. Then, crystallization wasconducted using a mixed solvent containing 300 ml of toluene and 200 mlof heptane, thereby obtaining 78 g of an objective compound(2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol) in the formof a colorless solid (yield: 67%, GC purity: 99%).

The results of instrumental analysis of the obtained compound were asfollows.

¹H-NMR: 1.59(d,2H,J=12.5 Hz), 1.64(s,3H),1.71-1.99(m,10H), 2.29(m,2H),2.63(t,1H,J=5.2 Hz), 4.29(d,2H,J=5.2 Hz), 4.67(s,2H)

¹³C-NMR: 22.35, 26.56, 27.26, 32.97, 34.54, 36.29, 38.05, 60.54, 61.50,89.87, 165.97, 172.81

GC-MS: 282(M+,0.02%), 165(0.09%), 149(40%), 148(100%), 133(22%),117(2.57%), 89(0.40%)

From the results above, it was confirmed that the obtained compound was2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol.

Subsequently, 165 g (584 mmol) of2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol, 2,000 ml ofTHF, 105 ml (754 mmol) of triethylamine, and 0.165 g (1,000 ppm) ofp-methoxyphenol were added to and dissolved in a 2L three-necked flaskequipped with a thermometer, a cooling pipe, and a stirrer.

Then, 62.7 ml (648 mmol) of methacryloyl chloride was gradually addedthereto while cooling in an ice bath. The temperature of the resultantwas elevated to room temperature, and the resultant was stirred for 3hours. Subsequently, 1,000 ml of diethylether was added thereto,followed by washing with 200 ml of distilled water 5 times. Thereafter,the extraction liquid was concentrated, thereby obtaining 198 g of anobjective compound (compound (11)) in the form of a colorless liquid(yield: 97%, GC purity: 99%).

The results of instrumental analysis of the obtained compound (11) wereas follows.

¹-NMR: 1.58(d,J=12.5 Hz,2H), 1.63(s,3H),1.71-1.89(m,8H), 1.98(s,3H),2.00(m,2H), 2.30(m,2H), 4.62(s,2H), 4.80(s,2H), 5.66(m,1H), 6.23(m,1H)

¹³C-NMR: 18.04, 22.15, 26.42, 27.14, 32.82, 34.38, 36.11, 37.92, 60.44,61.28, 89.42, 126.79, 135.18, 165.61, 166.30, 167.20

GC-MS: 350(M+,1.4%), 206(0.13%), 149(47%), 148(100%), 133(20%), 69(37%)

Monomer Synthesis Example 3 Synthesis of Compound (12)

The compound (12) used in the polymer synthesis examples described laterwas synthesized by a method described in paragraph [0070] of WO2007/94473.

Polymer Synthesis Example 1

In a three-necked flask equipped with a thermometer and a reflux tube,11.68 g (68.68 mmol) of a compound (1), 15.00 g (51.02 mmol) of acompound (2), 16.45 g (62.79 mmol) of a compound (3), 4.62 g (27.47mmol) of a compound (4) and 3.24 g (13.74 mmol) of a compound (5) weredissolved in 76.49 g of methyl ethyl ketone (MEK) to obtain a solution.Then, 20.13 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name:V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was addedand dissolved in the obtained solution.

The resultant was dropwise added to 42.49 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of an n-heptane/isopropylalcohol mixed solvent, and an operationto deposit a polymer was conducted. Thereafter, the precipitated whitepowder was separated by filtration, followed by washing with ann-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining30.82 g of a polymeric compound 1 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 9,900, and the dispersity was 1.45. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o/p=36.3/25.6/16.8/13.4/7.9.

Polymer Synthesis Example 2

In a three-necked flask equipped with a thermometer and a reflux tube,12.52 g (73.67 mmol) of a compound (1), 13.95 g (47.47 mmol) of acompound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48mmol) of a compound (4) were dissolved in 73.85 g of methyl ethyl ketone(MEK) to obtain a solution. Then, 21.8 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 40.96 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 34 g of a polymeric compound 2 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,700, and the dispersity was 1.65. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=38.2/28.5/21.0/12.3.

Polymer Synthesis Example 3

In a three-necked flask equipped with a thermometer and a reflux tube,11.00 g (64.73 mmol) of a compound (1), 13.95 g (47.47 mmol) of acompound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 101.04 g of methyl ethylketone (MEK) to obtain a solution. Then, 27.6 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 56.11 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 33 g of a polymeric compound 2 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,300, and the dispersity was 1.68. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=33.1/24.9/32.0/10.0.

Polymer Synthesis Example 4

In a three-necked flask equipped with a thermometer and a reflux tube,11.00 g (64.73 mmol) of a compound (1), 13.95 g (47.47 mmol) of acompound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 64.11 g of methyl ethyl ketone(MEK) to obtain a solution. Then, 20.9 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 35.60 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 31 g of a polymeric compound 4 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,800, and the dispersity was 1.63. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=32.9/24.8/32.1/10.2.

Polymer Synthesis Example 5

In a three-necked flask equipped with a thermometer and a reflux tube,15.37 g (69.23 mmol) of a compound (6), 13.95 g (47.47 mmol) of acompound (2), 16.58 g (63.29 mmol) of a compound (3), 4.65 g (27.69mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) weredissolved in 80.74 g of methyl ethyl ketone (MEK) to obtain a solution.Then, 22.2 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name:V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was addedand dissolved in the obtained solution.

The resultant was dropwise added to 44.84 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 37 g of a polymeric compound 5 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,600, and the dispersity was 1.70. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o/p=35.1/26.4/18.2/13.4/6.9.

Polymer Synthesis Example 6

In a three-necked flask equipped with a thermometer and a reflux tube,15.37 g (69.23 mmol) of a compound (6), 13.95 g (47.47 mmol) of acompound (2), 12.75 g (51.43 mmol) of a compound (7), 4.65 g (27.69mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) weredissolved in 75.00 g of methyl ethyl ketone (MEK) to obtain a solution.Then, 20.9 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name:V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was addedand dissolved in the obtained solution.

The resultant was dropwise added to 41.65 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 35 g of a polymeric compound 6 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,500, and the dispersity was 1.60. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o/p=34.3/25.7/19.5/12.9/7.6.

Polymer Synthesis Example 7

In a three-necked flask equipped with a thermometer and a reflux tube,16.02 g (72.15 mmol) of a compound (6), 13.95 g (47.47 mmol) of acompound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48mmol) of a compound (4) were dissolved in 79.00 g of methyl ethyl ketone(MEK) to obtain a solution. Then, 21.7 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 43.88 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 26 g of a polymeric compound 7 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,100, and the dispersity was 1.65. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=37.5/28.3/21.1/13.1.

Polymer Synthesis Example 8

In a three-necked flask equipped with a thermometer and a reflux tube,14.37 g (64.73 mmol) of a compound (6), 13.95 g (47.47 mmol) of acompound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 106.09 g of methyl ethylketone (MEK) to obtain a solution. Then, 27.6 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 58.92 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 35 g of a polymeric compound 8 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,000, and the dispersity was 1.62.

Further, as a result of an analysis by carbon 13 nuclear magneticresonance spectroscopy (600 MHz, ¹³C-NMR), it was found that thecomposition of the copolymer (ratio (molar ratio) of the respectivestructural units within the structural formula) wasl/m/n/o=33.2/25.3/31.4/10.1.

Polymer Synthesis Example 9

In a three-necked flask equipped with a thermometer and a reflux tube,14.37 g (64.73 mmol) of a compound (6), 13.95 g (47.47 mmol) of acompound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 69.16 g of methyl ethyl ketone(MEK) to obtain a solution. Then, 20.9 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 38.41 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 32 g of a polymeric compound 9 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,600, and the dispersity was 1.67. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=33.0/25.1/32.1/9.8.

Polymer Synthesis Example 10

In a three-necked flask equipped with a thermometer and a reflux tube,17.72 g (63.29 mmol) of a compound (8), 13.95 g (47.47 mmol) of acompound (2), 16.58 g (63.29 mmol) of a compound (3), 4.65 g (27.69mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) weredissolved in 84.26 g of methyl ethyl ketone (MEK) to obtain a solution.Then, 25.9 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name:V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was addedand dissolved in the obtained solution.

The resultant was dropwise added to 46.81 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 39 g of a polymeric compound 10 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,900, and the dispersity was 1.63. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o/p=35.1/26.2/18.2/13.7/6.8.

Polymer Synthesis Example 11

In a three-necked flask equipped with a thermometer and a reflux tube,17.85 g (63.29 mmol) of a compound (9), 13.95 g (47.47 mmol) of acompound (2), 16.58 g (63.29 mmol) of a compound (3), 4.65 g (27.69mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) weredissolved in 84.46 g of gamma-butyrolactone (GBL) to obtain a solution.Then, 25.9 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name:V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was addedand dissolved in the obtained solution.

The resultant was dropwise added to 46.91 g of GBL heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with ann-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining39 g of a polymeric compound 11 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,500, and the dispersity was 1.68. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o/p=35.3/26.6/18.2/13.6/6.3.

Polymer Synthesis Example 12

In a three-necked flask equipped with a thermometer and a reflux tube,14.62 g (65.27 mmol) of a compound (10), 13.95 g (47.47 mmol) of acompound (2), 16.58 g (63.29 mmol) of a compound (3), 4.65 g (27.69mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) weredissolved in 79.62 g of gamma-butyrolactone (GBL) to obtain a solution.Then, 26.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name:V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was addedand dissolved in the obtained solution.

The resultant was dropwise added to 44.21 g of GBL heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with ann-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining37 g of a polymeric compound 12 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,700, and the dispersity was 1.67. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o/p=35.6/26.2/18.1/13.5/6.6.

Polymer Synthesis Example 13

In a three-necked flask equipped with a thermometer and a reflux tube,15.31 g (68.36 mmol) of a compound (10), 13.95 g (47.47 mmol) of acompound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48mmol) of a compound (4) were dissolved in 77.94 g of gamma-butyrolactone(GBL) to obtain a solution. Then, 25.5 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 43.28 g of GBL heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with ann-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining36 g of a polymeric compound 13 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,300, and the dispersity was 1.66. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=37.9/28.3/21.0/12.8.

Polymer Synthesis Example 14

In a three-necked flask equipped with a thermometer and a reflux tube,14.50 g (64.73 mmol) of a compound (10), 13.95 g (47.47 mmol) of acompound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 106.92 g ofgamma-butyrolactone (GBL) to obtain a solution. Then, 27.6 mmol ofdimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured byWako Pure Chemical Industries, Ltd.) was added and dissolved in theobtained solution.

The resultant was dropwise added to 59.03 g of GBL heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with ann-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining35 g of a polymeric compound 14 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,600, and the dispersity was 1.64. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=33.1/25.4/31.3/10.2.

Polymer Synthesis Example 15

In a three-necked flask equipped with a thermometer and a reflux tube,14.50 g (64.73 mmol) of a compound (10), 13.95 g (47.47 mmol) of acompound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 69.36 g of gamma-butyrolactone(GBL) to obtain a solution. Then, 25.1 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 38.51 g of GBL heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 32 g of a polymeric compound 15 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,900, and the dispersity was 1.62. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=32.9/24.8/32.6/9.7.

Polymer Synthesis Example 16

In a three-necked flask equipped with a thermometer and a reflux tube,18.74 g (66.46 mmol) of a compound (9), 13.95 g (47.47 mmol) of acompound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48mmol) of a compound (4) were dissolved in 83.08 g of gamma-butyrolactone(GBL). Then, 21.7 mmol of dimethyl 2,2′-azobis(isobutyrate) (productname: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) wasadded and dissolved in the obtained solution.

The resultant was dropwise added to 46.14 g of GBL heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 38 g of a polymeric compound 16 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,500, and the dispersity was 1.67. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=38.0/27.8/20.8/13.4.

Polymer Synthesis Example 17

In a three-necked flask equipped with a thermometer and a reflux tube,18.25 g (64.73 mmol) of a compound (9), 13.95 g (47.47 mmol) of acompound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 111.91 g ofgamma-butyrolactone (GBL) to obtain a solution. Then, 33.1 mmol ofdimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured byWako Pure Chemical Industries, Ltd.) was added and dissolved in theobtained solution.

The resultant was dropwise added to 62.16 g of GBL heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with ann-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining37 g of a polymeric compound 17 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,200, and the dispersity was 1.67. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=33.5/25.4/31.0/10.1.

Polymer Synthesis Example 18

In a three-necked flask equipped with a thermometer and a reflux tube,18.25 g (64.73 mmol) of a compound (9), 13.95 g (47.47 mmol) of acompound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 74.98 g of gamma-butyrolactone(GBL) to obtain a solution. Then, 25.1 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 41.64 g of GBL heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with ann-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining35 g of a polymeric compound 18 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,600, and the dispersity was 1.62. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=33.3/24.7/33.1/8.9.

Polymer Synthesis Example 19

In a three-necked flask equipped with a thermometer and a reflux tube,18.61 g (66.46 mmol) of a compound (8), 13.95 g (47.47 mmol) of acompound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48mmol) of a compound (4) were dissolved in 82.89 g of methyl ethyl ketone(MEK) to obtain a solution. Then, 21.7 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 46.03 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 38 g of a polymeric compound 19 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,300, and the dispersity was 1.66. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=38.1/28.2/20.1/13.6.

Polymer Synthesis Example 20

In a three-necked flask equipped with a thermometer and a reflux tube,18.12 g (64.73 mmol) of a compound (8), 13.95 g (47.47 mmol) of acompound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 111.72 g of methyl ethylketone (MEK) to obtain a solution. Then, 33.1 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 62.05 g of MEK heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 52 g of a polymeric compound 20 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,000, and the dispersity was 1.67. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=33.5/25.3/30.9/10.3.

Polymer Synthesis Example 21

In a three-necked flask equipped with a thermometer and a reflux tube,18.12 g (64.73 mmol) of a compound (8), 13.95 g (47.47 mmol) of acompound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58mmol) of a compound (5) were dissolved in 74.79 g of methyl ethyl ketone(MEK) to obtain a solution. Then, 25.1 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 41.53 g of MEK heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with ann-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining35 g of a polymeric compound 21 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,800, and the dispersity was 1.67. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=33.2/24.7/32.8/9.3.

Polymer Synthesis Example 22

In a three-necked flask equipped with a thermometer and a reflux tube,7.85 g (46.16 mmol) of a compound (1), 9.31 g (31.65 mmol) of a compound(2), 8.50 g (34.29 mmol) of a compound (7), 3.10 g (18.46 mmol) of acompound (4) and 2.18 g (9.23 mmol) of a compound (5) were dissolved in45.85 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 14.0mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601,manufactured by Wako Pure Chemical Industries, Ltd.) was added anddissolved in the obtained solution.

The resultant was dropwise added to 25.47 g of MEK heated to 78° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/isopropylalcohol mixedsolvent and drying, thereby obtaining 21 g of a polymeric compound 22 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,700, and the dispersity was 1.53.

Further, as a result of an analysis by carbon 13 nuclear magneticresonance spectroscopy (600 MHz, ¹³C-NMR), it was found that thecomposition of the copolymer (ratio (molar ratio) of the respectivestructural units within the structural formula) wasl/m/n/o/p=34.7/26.2/19.1/12.5/7.5.

Polymer Synthesis Example 23

In a three-necked flask equipped with a thermometer and a reflux tube,19.97 g (67.94 mmol) of a compound (2), 12.36 g (35.33 mmol) of acompound (11), 20.00 g (108.70 mmol) of a compound (12) and 11.54g(48.92 mmol) of a compound (5) were dissolved in 94.61 g of propyleneglycol methyl ether acetate (PM). Then, 26.1 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 52.55 g of PM heated to 80° C. in anitrogen atmosphere over 6 hours.

Thereafter, the reaction solution was heated for 1 hour while stirring,and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with a methanol/water mixedsolvent and drying, thereby obtaining 44 g of a polymeric compound 23 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 10,500, and the dispersity was 1.47.

Further, as a result of an analysis by carbon 13 nuclear magneticresonance spectroscopy (600 MHz, ¹³C-NMR), it was found that thecomposition of the copolymer (ratio (molar ratio) of the respectivestructural units within the structural formula) wasl/m/n/o=28.0/14.2/36.0/21.8.

Polymer Synthesis Example 24

In a three-necked flask equipped with a thermometer and a reflux tube,12.82 g (43.62 mmol) of a compound (2), 5.10 g (17.45 mmol) of acompound (13), 80.00 g (305.34 mmol) of a compound (3) and 4.12 g (17.45mmol) of a compound (5) were dissolved in 152.28 g of propylene glycolmethyl ether acetate (PM). Then, 15.4 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 84.60 g of PM heated to 80° C. in anitrogen atmosphere over 3 hours.

Thereafter, the reaction solution was heated for 4 hour while stirring,and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with a methanol/n-heptane mixed solventand drying, thereby obtaining 23 g of a polymeric compound 24 as anobjective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 6,400, and the dispersity was 1.29. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=28.1/9.5/47.6/14.8.

Polymer Synthesis Example 25

In a three-necked flask equipped with a thermometer and a reflux tube,10.13 g (34.46 mmol) of a compound (2), 4.53 g (15.51 mmol) of acompound (13), 20.00 g (108.54 mmol) of a compound (12) and 3.66 g(15.51 mmol) of a compound (5) were dissolved in 56.87 g of propyleneglycol methyl ether acetate (PM). Then, 17.4 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 31.59 g of PM heated to 80° C. in anitrogen atmosphere over 6 hours.

Thereafter, the reaction solution was heated for 1 hour while stirring,and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with a 2-propanol/n-heptane mixedsolvent and drying, thereby obtaining 27 g of a polymeric compound 25 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 9,700, and the dispersity was 1.65. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=22.4/9.1/56.8/11.7.

Polymer Synthesis Example 26

In a three-necked flask equipped with a thermometer and a reflux tube,9.30 g (31.65 mmol) of a compound (2), 9.10 g (38.88 mmol) of a compound(14) and 4.05 g (17.18 mmol) of a compound (5) were dissolved in 33.12 gof methyl ethyl ketone (MEK) to obtain a solution. Then, 5.8 mmol ofdimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured byWako Pure Chemical Industries, Ltd.) was added and dissolved in theobtained solution.

The resultant was dropwise added to 18.40 g of MEK heated to 78° C. in anitrogen atmosphere over 6 hours. Thereafter, the reaction solution washeated for 1 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with a methanol/water mixedsolvent and drying, thereby obtaining 15 g of a polymeric compound 26 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 9,100, and the dispersity was 1.53. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n=39.7/41.2/19.1.

Polymer Synthesis Example 27

In a three-necked flask equipped with a thermometer and a reflux tube,9.30 g (31.65 mmol) of a compound (2), 6.53 g (38.88 mmol) of a compound(4) and 4.05 g (17.18 mmol) of a compound (5) were dissolved in 29.27 gof methyl ethyl ketone (MEK) to obtain a solution. Then, 7.0 mmol ofdimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured byWako Pure Chemical Industries, Ltd.) was added and dissolved in theobtained solution.

The resultant was dropwise added to 16.25 g of MEK heated to 78° C. in anitrogen atmosphere over 6 hours. Thereafter, the reaction solution washeated for 1 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with a methanol/water mixedsolvent and drying, thereby obtaining 14 g of a polymeric compound 27 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 9,400, and the dispersity was 1.51. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n=39.5/41.0/19.5.

Polymer Synthesis Example 28

In a three-necked flask equipped with a thermometer and a reflux tube,12.82 g (43.62 mmol) of a compound (2), 80.00 g (305.34 mmol) of acompound (3), 2.93 g (17.45 mmol) of a compound (4) and 4.12 g (17.45mmol) of a compound (5) were dissolved in 149.81 g of methyl ethylketone (MEK) to obtain a solution. Then, 15.4 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 83.22 g of MEK heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with a methanol/n-heptane mixed solventand drying, thereby obtaining 25 g of a polymeric compound 28 as anobjective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 6,300, and the dispersity was 1.41. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=27.4/48.6/9.7/14.3.

Comparative Polymer Synthesis Example 1

In a three-necked flask equipped with a thermometer and a reflux tube,10.29 g (43.62 mmol) of a compound (15), 80.00 g (305.34 mmol) of acompound (3), 2.93 g (17.45 mmol) of a compound (4) and 4.12 g (17.45mmol) of a compound (5) were dissolved in 146.01 g of methyl ethylketone (MEK) to obtain a solution. Then, 15.4 mmol of dimethyl2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako PureChemical Industries, Ltd.) was added and dissolved in the obtainedsolution.

The resultant was dropwise added to 81.12 g of MEK heated to 80° C. in anitrogen atmosphere over 3 hours. Thereafter, the reaction solution washeated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with a methanol/n-heptane mixed solventand drying, thereby obtaining 25 g of a polymeric compound 29 as anobjective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 6,300, and the dispersity was 1.41. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o=27.4/48.6/9.7/14.3.

Comparative Polymer Synthesis Example 2

In a three-necked flask equipped with a thermometer and a reflux tube,7.47 g (31.65 mmol) of a compound (15), 9.10 g (38.88 mmol) of acompound (14) and 4.05 g (17.18 mmol) of a compound (5) were dissolvedin 30.93 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 5.8mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601,manufactured by Wako Pure Chemical Industries, Ltd.) was added anddissolved in the obtained solution.

The resultant was dropwise added to 17.18 g of MEK heated to 78° C. in anitrogen atmosphere over 6 hours. Thereafter, the reaction solution washeated for 1 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of a methanol/water mixed solvent, and an operation to deposit apolymer was conducted. Thereafter, the precipitated white powder wasseparated by filtration, followed by washing with a methanol/water mixedsolvent and drying, thereby obtaining 14 g of a polymeric compound 30 asan objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 8,900, and the dispersity was 1.51. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n=39.8/41.2/19.0.

Polymer Synthesis Example 29

The same procedure as in the aforementioned polymer synthesis exampleswas performed, except that the compound (2′) and the compound (16) wereused in predetermined molar ratio, thereby obtaining a polymericcompound 31 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,300, and the dispersity was 1.6. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m=50/50.

Measurement of Receding Angle

100 parts by weight of each of the polymeric compounds 1, 5, 10 to 12and 28 was individually dissolved in 2,500 parts by weight of aPGMEA/PGME mixed solvent (weight ratio: PGMEA/PGME=6/4), therebyobtaining a resin solution. Then, using a spinner, each of the resinsolutions was applied onto an 8-inch silicon wafer that had been treatedwith hexamethyldisilazane (HMDS), and the solution was then prebaked(PAB) and dried on a hotplate at 110° C. for 60 seconds, thus forming aresin film with a film thickness of 120 nm.

A water droplet was dripped onto the surface of each resin film, and aDROP MASTER-700 apparatus (a product name, manufactured by KyowaInterface Science Co. Ltd.) was used to measure the receding angle(receding angle measurement: water 50 μl). The measured value wasdefined as the “receding angle (°) prior to development”. Subsequently,the wafer which had been subjected to the measurement of contact anglewas subjected to an alkali developing treatment for 30 seconds at 23° C.in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH), and the receding angle was measured in the same manner asdescribed above. The measured value was defined as the “receding angle(°) after 30 seconds development”. The results are shown in Table 1.

TABLE 1 Receding angle Receding angle after 30 prior to seconds ΔReceding development development angle (°) (°) (°) Polymeric compound 155.0 32.1 22.9 Polymeric compound 5 54.3 36.8 17.5 Polymeric compound 1054.1 37.1 17.0 Polymeric compound 11 54.9 31.8 23.1 Polymeric compound12 54.5 32.3 22.2 Polymeric compound 28 65.6 50.6 15.0

From the results shown above, it was found that, when the resincontained both of the structural unit (a0) and the structural unit (a2),the hydrophilicity thereof changed significantly by coming in contactwith an alkali developing solution, and it was confirmed that thehydrophilicity of the film surface became significantly high after 30seconds development. These results show that generation of defectsfollowing development caused by high water repellency of the resist filmsurface can be reduced.

Examples 1 to 28, Comparative Examples 1 and 2

100 parts by weight of the component (A) shown in Table 2, 9.8 parts byweight of a compound represented by chemical formula (B)-1 shown below,0.4 parts by weight of tri-n-pentylamine, 10 parts by weight ofγ-butyrolactone and 2,500 parts by weight of a PGMEA/PGME mixed solvent(PGMEA/PGME=6/4 (weight ratio)) were mixed together and dissolved toobtain a positive resist composition.

Using the obtained resist compositions, the following evaluations wereconducted.

(Formation of Resist Pattern)

An organic anti-reflection film composition (product name: ARC95,manufactured by Brewer Science Ltd.) was applied onto an 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 89 nm. Then, each of the resist compositions obtainedabove was applied onto the anti-reflection film using a spinner, and wasthen prebaked (PAB) on a hotplate at a temperature indicated in Table 2for 60 seconds and dried, thereby forming a resist film having a filmthickness of 100 nm.

Subsequently, a coating solution for forming a protection film (productname: TILC-057; manufactured by Tokyo Ohka Kogyo Co., Ltd.) was appliedonto the resist film using a spinner, and then heated at 90° C. for 60seconds, thereby forming a top coat with a film thickness of 35 nm.

Thereafter, using an ArF exposure apparatus for immersion lithography(product name: NSR-S609B, manufactured by Nikon Corporation, NA(numerical aperture) =1.07, 2/3 annular illumination, reduction ratio:1/4, immersion medium: water), the resist film having a top coat formedthereon was selectively irradiated with an ArF excimer laser (193 nm)through a mask pattern targeting a contact hole pattern with a holediameter of 90 nm and a pitch of 140 nm (hereafter, this contact holepattern is referred to as “CH pattern”).

Next, a post exposure bake (PEB) treatment was conducted at atemperature indicated in Table 2 for 60 seconds, followed by developmentfor 60 seconds at 23° C. in a 2.38% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) (product name: NMD-3; manufacturedby Tokyo Ohka Kogyo Co., Ltd.). Then, the resist film was rinsed for 30seconds with pure water, followed by drying by shaking.

As a result, in each of the examples, a CH pattern was formed.

(Evaluation of Pattern Shape)

Each of the CH patterns formed in the (Formation of resist pattern) wasobserved from the upper side thereof using a scanning electronmicroscope (SEM), and the circularity was evaluated with the followingcriteria.

The results are shown in Table 2.

A: no unevenness was observed at the circumferential portions of thehole pattern, and the pattern shape was excellent

B: unevenness was observed at some circumferential portions of the holepattern

C: a part of the circumferential portion of the hole pattern wasdistorted

D: the entire circumferential portion of the hole pattern was distorted

TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Component PolymericPolymeric Polymeric Polymeric Polymeric Polymeric (A) compound 1compound 2 compound 3 compound 4 compound 5 compound 6 PAB/PEB 90/8590/85 90/85 110/110 90/85 100/95  [° C.] Circularity A A B B A A Ex. 7Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Component Polymeric Polymeric PolymericPolymeric Polymeric Polymeric (A) compound 7 compound 8 compound 9compound 10 compound 11 compound 12 PAB/PEB 90/85 90/85 110/110 90/8590/85 90/85 [° C.] Circularity A B B A A A Ex. 13 Ex. 14 Ex. 15 Ex. 16Ex. 17 Ex. 18 Component Polymeric Polymeric Polymeric PolymericPolymeric Polymeric (A) compound 13 compound 14 compound 15 compound 16compound 17 compound 18 PAB/PEB 90/85 90/85 110/110 90/85 90/85 110/110[° C.] Circularity A B B A B B Ex. 19 Ex. 20 Ex. 21 Ex. 22 Ex. 23 Ex. 24Component Polymeric Polymeric Polymeric Polymeric Polymeric Polymeric(A) compound 19 compound 20 compound 21 compound 22 compound 23 compound24 PAB/PEB 90/85 90/85 110/110 100/95  110/110 90/85 [° C.] CircularityA B B A A A Ex. 25 Ex. 26 Ex. 27 Ex. 28 Comp. Ex. 1 Comp. Ex. 2Component Polymeric Polymeric Polymeric Polymeric Polymeric Polymeric(A) compound 25 compound 26 compound 27 compound 28 compound 29 compound30 PAB/PEB 110/110 110/110 110/110 90/85 90/85 110/110 [° C.]Circularity A B B A C D

As seen from the results, the resist patterns formed using the resistcompositions of Examples 1 to 28 had an excellent shape.

Example 29

The components shown in Table 3 below, γ-butyrolactone (10 parts byweight) and a mixed solvent of PGMEA and PGME (PGMEA/PGME=6/4 (weightratio)) (2,500 parts by weight) were mixed together and dissolved toobtain a positive resist composition.

TABLE 3 Component Component Component Other (A) (B) (D) additive Ex. 29(A)-29 (B)-2 (B)-3 (D)-2 (F)-1 [100] [9.5] [2.0] [0.6] [1.5]

In Table 3, the reference characters indicate the following. Further,the values in brackets [ ] indicate the amount (in terms of parts byweight) of the component added.

(A)-29: the aforementioned polymeric compound 31

(B)-2: a compound represented by formula (B)-2 shown below

(B)-3: a compound represented by formula (B)-3 shown below

(D)-2: 1,8-naphthalenediamine

(F)-1: a fluorine-containing polymeric compound represented by formula(F)-1 shown below. Mw=25,000, Mw/Mn=1.5, compositional ratio of thecopolymer (ratio (molar ratio) of the respective structural units withinthe structural formula): l/m=80/20

Using the obtained resist compositions, resist patterns were formed inthe following manner, and evaluations were performed as follows.

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied onto an 8-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 77 nm. Then, the resist composition was applied ontothe anti-reflection film using a spinner, and was then prebaked (PAB) ona hotplate at 120° C. for 60 seconds and dried, thereby forming a resistfilm having a film thickness of 100 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask pattern, using an ArF exposureapparatus NSR-S302A (manufactured by Nikon Corporation; NA (numericalaperture)=0.6, annu.). Thereafter, a post exposure bake (PEB) treatmentwas conducted at 95° C. for 60 seconds, followed by alkali developmentfor 30 seconds at 23° C. in a 2.38% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) (product name: NMD-3; manufacturedby Tokyo Ohka Kogyo Co., Ltd.). Then, the resist was washed for 25seconds with pure water, followed by drying by shaking.

As a result, a line and space pattern (L/S pattern) in which lineshaving a line width of 130 nm were arranged at equal intervals (pitch:260 nm) was formed on the resist film. The optimum exposure dose Eop(mJ/cm²; sensitivity) for forming the L/S pattern was found to be 41mJ/cm². Further, the cross-sectional shape of the obtained L/S patternwas observed using a scanning electron microscope (SEM) (product name:SEM S-9220, manufactured by Hitachi, Ltd.). As a result, it was foundthat the pattern exhibited an excellent rectangularity.

[Synthesis of Fluorine-Containing Polymeric Compound (F)-1]

The aforementioned (F)-1 was synthesized as follows.

(1. Synthesis of Compound (f111))

61 g (600 mmol) of triethylamine and 64 g (418 mmol) of methylbromoacetate were added to 300 ml of a THF solution containing 30 g (348mmol) of methacrylic acid in a nitrogen atmosphere at 0° C., and thetemperature was elevated to room temperature, followed by stirring for 3hours. After conducting thin-layer chromatography to confirm that theraw materials had been consumed, the reaction solution was subjected todistillation under reduced pressure to remove the solvent. Then, waterwas added to the resultant, and extraction was conducted with ethylacetate three times. The resulting organic phase was washed with watertwice, and then subjected to distillation under reduced pressure toremove the solvent, thereby obtaining 47 g of a compound (21)-1 in theform of a colorless liquid (yield: 85%).

Subsequently, 700 ml of a THF solution containing 30 g (190 mmol) of thecompound (21)-1 was prepared, and 700 ml of a 2.38% by weight aqueoussolution of TMAH was added thereto, followed by stirring at roomtemperature for 3 hours. After conducting thin-layer chromatography toconfirm that the raw materials had been consumed, THF was distilled offunder reduced pressure. Then, the resulting aqueous reaction solutionwas cooled to 0° C., and 50 ml of a 10N hydrochloric acid was addedthereto to render the aqueous reaction solution acidic, followed byextraction with ethyl acetate three times. The resulting organic phasewas washed with water twice, and the solvent was distilled off underreduced pressure, thereby obtaining 26 g of a compound (21)-2 in theform of a colorless liquid (yield: 95%).

Next, 26 g (180.39 mmol) of the compound (21)-2 was added to 200 ml of aTHF solution containing 23.48 g (234.5 mmol) of 2,2,2-trifluoroethanol(CF₃CH₂OH), 51.9 g (270.6 mmol) of ethyldiisopropylaminocarbodiimidehydrochloride (EDCl) and 0.11 g (0.9 mmol) of dimethylaminopyridine(DMAP) in a nitrogen atmosphere at 0° C., and the temperature waselevated to room temperature, followed by stirring for 3 hours. Afterconducting thin-layer chromatography to confirm that the raw materialshad been consumed, the reaction solution was cooled to 0° C., and waterwas added thereto to stop the reaction. Then, extraction was conductedwith ethyl acetate three times, and the obtained organic phase waswashed with water twice. Thereafter, the solvent was distilled off underreduced pressure to obtain a crude product, and the obtained crudeproduct was purified by silica gel filtration (using ethyl acetate),thereby obtaining 25 g of the objective compound (f111) in the form of acolorless liquid.

The obtained compound (f111) was analyzed by ¹H-NMR to confirm itsstructure.

The results of the ¹H-NMR analysis are shown below.

¹H-NMR(CDCl₃,400 MHz):δ(ppm)=6.24(s,1H,Hb), 5.70(s,1H,Hb),4.80(s,2H,Hc), 4.60-4.51(m,2H,Hd), 1.99(s,3H,Ha)

(2. Synthesis of (F)-1)

15.00 g (54.32 mmol) of the compound (f111) and 5.21 g (23.28 mmol) ofthe compound (f211) were added to a three-necked flask equipped with athermometer and a reflux tube and were dissolved by adding 114.52 g ofTHF thereto. Then, 4.66 mmol of dimethyl 2,2′-azobis(isobutyrate)(V-601) was added and dissolved in the obtained solution. The solutionwas stirred while heating at 80° C. for 6 hours in a nitrogenatmosphere, and was then cooled to room temperature. The resultingpolymer solution was concentrated under reduced pressure, and dropwiseadded to an excess amount of n-heptane to thereby precipitate a polymer.Then, the precipitated polymer was separated by filtration, followed bywashing and drying, thereby obtaining 5.6 g of a fluorine-containingpolymeric compound (F)-1 as an objective compound.

With respect to the obtained fluorine-containing polymeric compound, theweight average molecular weight (Mw) and the dispersity (Mw/Mn) weredetermined by the polystyrene equivalent value as measured by gelpermeation chromatography (GPC). As a result, it was found that theweight average molecular weight was 25,000, and the dispersity was 1.5.Further, as a result of an analysis by carbon 13 nuclear magneticresonance spectroscopy (600 MHz, ¹³C-NMR), it was found that thecomposition of the copolymer (ratio (molar ratio) of the respectivestructural units within the structural formula) was l/m=80/20.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

1. A positive resist composition comprising a base component (A) whichexhibits increased solubility in an alkali developing solution underaction of acid and an acid-generator component (B) which generates acidupon exposure, said component (A) comprising: a polymeric compound (A1′)comprising a structural unit (a0) represented by general formula (a0-1)shown below and a structural unit (a2) derived from an acrylate estercontaining a lactone-containing cyclic group exclusive of saidstructural unit (a0), said polymeric compound (A1′) containing an aciddissociable, dissolution inhibiting group within the structure thereof;or a polymeric compound (A1) comprising a structural unit (a0)represented by general formula (a0-1) shown below and a structural unit(a1) derived from an acrylate ester containing an acid dissociable,dissolution inhibiting group exclusive of said structural unit (a0) andsaid structural unit (a2).

wherein R¹ represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R² represents a divalent linking group;each R′ independently represents a hydrogen atom, an alkyl group of 1 to6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or —COOR″,wherein R″ represents a hydrogen atom or an alkyl group; and A″represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5carbon atoms which may contain an oxygen atom or a sulfur atom.
 2. Thepositive resist composition according to claim 1, wherein saidstructural unit (a1) comprises at least two types of structural units.3. The positive resist composition according to claim 1, wherein saidstructural unit (a1) comprises at least one member selected from thegroup consisting of a structural unit represented by general formula(a1-0-11) shown below, a structural unit represented by general formula(a1-0-12) shown below and a structural unit represented by generalformula (a1-0-2) shown below:

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R²¹ represents an alkyl group; R²²represents a group which forms an aliphatic monocyclic group with thecarbon atom to which R²² is bonded; R²³ represents a branched alkylgroup; R²⁴ represents a group which forms an aliphatic polycyclic groupwith the carbon atom to which R²⁴ is bonded; Y² represents a divalentlinking group; and X² represents an acid dissociable, dissolutioninhibiting group.
 4. The positive resist composition according to claim1, wherein the total amount of said structural unit (a0) and saidstructural unit (a2) within said polymeric compound (A1′) is 5 to 70 mol%.
 5. The positive resist composition according to claim 1, wherein saidstructural unit (a2) comprises at least one member selected from thegroup consisting of a structural unit represented by general formula(a2-1) shown below and a structural unit represented by general formula(a2-2) shown below:

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; each R′ independently represents ahydrogen atom, an alkyl group of 1 to 5 carbon atoms, an alkoxy group of1 to 5 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom oran alkyl group; R²⁹ represents a single bond or a divalent linkinggroup; s″ represents an integer of 0 to 2; and A″ represents an oxygenatom, a sulfur atom or an alkylene group of 1 to 5 carbon atoms whichmay contain an oxygen atom or a sulfur atom.
 6. The positive resistcomposition according to claim 1, wherein said polymeric compound (A1′)further comprises said structural unit (a1).
 7. The positive resistcomposition according to claim 1, wherein said polymeric compound (A1)or said polymeric compound (A1′) further comprises a structural unit(a3) derived from an acrylate ester containing a polar group-containingaliphatic hydrocarbon group.
 8. The positive resist compositionaccording to claim 1, which further comprises a nitrogen-containingorganic compound (D).
 9. A method of forming a resist pattern,comprising: applying a positive resist composition of claim 1 to asubstrate to form a resist film on the substrate; conducting exposure ofsaid resist film; and alkali-developing said resist film to form aresist pattern.
 10. A polymeric compound comprising: a component (A1′)comprising a structural unit (a0) represented by general formula (a0-1)shown below and a structural unit (a2) derived from an acrylate estercontaining a lactone-containing cyclic group exclusive of saidstructural unit (a0), said component (A1′) containing an aciddissociable, dissolution inhibiting group within the structure thereof;or a component (A1) comprising a structural unit (a0) represented bygeneral formula (a0-1) shown below and a structural unit (a1) derivedfrom an acrylate ester containing an acid dissociable, dissolutioninhibiting group exclusive of said structural unit (a0) and saidstructural unit (a2):

wherein R¹ represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R² represents a divalent linking group;each R′ independently represents a hydrogen atom, an alkyl group of 1 to6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or —COOR″,wherein R″ represents a hydrogen atom or an alkyl group; and A″represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5carbon atoms which may contain an oxygen atom or a sulfur atom.
 11. Thepolymeric compound according to claim 10, wherein said structural unit(a1) comprises at least two types of structural units.
 12. The polymericcompound according to claim 10, wherein said structural unit (a1)comprises at least one member selected from the group consisting of astructural unit represented by general formula (a1-0-11) shown below, astructural unit represented by general formula (a1-0-12) shown below anda structural unit represented by general formula (a1-0-2) shown below:

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R²¹ represents an alkyl group; R²²represents a group which forms an aliphatic monocyclic group with thecarbon atom to which R²² is bonded; R²³ represents a branched alkylgroup; R²⁴ represents a group which forms an aliphatic polycyclic groupwith the carbon atom to which R²⁴ is bonded; Y² represents a divalentlinking group; and X² represents an acid dissociable, dissolutioninhibiting group.
 13. The polymeric compound according to claim 10,wherein the total amount of said structural unit (a0) and saidstructural unit (a2) within said component (A1′) is 5 to 70 mol %. 14.The polymeric compound according to claim 10, wherein said structuralunit (a2) comprises at least one member selected from the groupconsisting of a structural unit represented by general formula (a2-1)shown below and a structural unit represented by general formula (a2-2)shown below:

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; each R′ independently represents ahydrogen atom, an alkyl group of 1 to 5 carbon atoms, an alkoxy group of1 to 5 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom oran alkyl group; R²⁹ represents a single bond or a divalent linkinggroup; s″ represents an integer of 0 to 2; and A″ represents an oxygenatom, a sulfur atom or an alkylene group of 1 to 5 carbon atoms whichmay contain an oxygen atom or a sulfur atom.
 15. The polymeric compoundaccording to claim 10, wherein said component (A1′) further comprisessaid structural unit (a1).
 16. The polymeric compound according to claim10, which further comprises a structural unit (a3) derived from anacrylate ester containing a polar group-containing aliphatic hydrocarbongroup.